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TOPIC 5: Atoms, Molecules, & Ions The History of Atomic Theories PLUM PUDDING MODEL 1. Democritus (Greek Philosopher - 15th Century B.C) - coined the term “atomos”, means “uncuttable” or “indivisible”. - believed all matter consists of very small indivisible particles....

TOPIC 5: Atoms, Molecules, & Ions The History of Atomic Theories PLUM PUDDING MODEL 1. Democritus (Greek Philosopher - 15th Century B.C) - coined the term “atomos”, means “uncuttable” or “indivisible”. - believed all matter consists of very small indivisible particles. ✅ Recognized electrons as components - all matter could be subdivided only until some finite particle is reached. of atoms - tearing of paper ❌ No nucleus, and didn’t explain later 2. John Dalton (English Scientist, Teacher - experimental observations. 1808) - atoms are indivisible building blocks of 2. Ernest Rutherford (1911) matter. - positively charged particles and most of HYPOTHESIS: the mass of an atom were concentrated in an - elements are composed of extremely extremely small volume called nucleus. small particles. - The empty space around the nucleus is - compounds are composed of atoms called the extranuclear part, where of more than 1 element. electrons are present. - all atoms of a given element are identical (same size, mass, & NUCLEAR MODEL chemical properties). - atoms of one element are different from other elements. - chemical reaction involves only the separation, combination, or rearrangement of atoms; does not result in their creation or destruction. ✅ Realised that positive charge was SOLID SPHERE MODEL ✅ Atoms of a particular element differ localised in the nucleus of an atom. from other elements. ❌ Did not explain why electrons remain ❌ Atoms aren’t indivisible — they’re in orbit around the nucleus. composed from subatomic particles. 3. Neils Bohr (Danish Physicist - 1913) - electrons moved around the nucleus in 1. J.J Thomson (British Physicist - 1898) orbits of fixed size and energies. - atom possesses a spherical shape in which the positive charge is uniformly distributed. PLANETARY MODEL - resembles pudding with plums or watermelon of positive charge with seeds (electrons). ✅ Stable electron orbits; explained emission spectra of some elements. ❌ Moving electrons should emit energy ➔ mass of proton is approximately 1.672 x 10-24 and collapse into the nucleus. Model did ➔ Protons are 1800 times heavier than not work well for heavier atoms. electrons. ➔ ** Total no. of protons in the atoms of an element = Atomic number of the element ** 4. Erwin Schrodinger (Austrian Physicist - 1926) - assumes electron is a wave Neutron (=) - tries to describe regions in space, or ➔ electrically neutral particles that orbitals, where electrons are most likely to carry no charge be found. ➔ have a mass slightly greater than that of protons. QUANTUM MODEL ➔ mass of neutron is almost same as proton, 1.674 x 10-24 ➔ different isotopes of an element have the same number of protons but vary in the number of neutrons present in the nuclei. ✅ Shows electrons don’t move around the nucleus in orbits, but in clouds where Charge their position is uncertain. Particle Mass (g) Coulom Charge ✅ Widely accepted as the most accurate b Unit model of an atom. Electron 9.1 x 10-31 - 1.602 x -1 10-19 Atomic Structure Proton 1.672 x 10- + 1.602 +1 ★ Atom - basic unit of an element that 24 x 10-19 can enter into chemical combination. ★ Subatomic Particles - atoms possess Neutron 1.674 x 10- 0 0 internal structure; they are made up 24 of smaller particles. ○ Electron Types of Rays / Radioactive Radiation ○ Proton 1. Alpha Rays / α particles - consists ○ Neutron of positively charged particles Subatomic Particles (protons) and are deflected by the Electron (-) positively charged plate. ➔ negatively charged particles 2. Beta Rays / β particles - consists of ➔ charge of electron: -1e, negatively charged particles approximates to -1.602 x 10-19 (electrons) and are deflected by the ➔ mass of electron is approximately negatively charged plate. 9.1 x 10-31 3. Gamma Rays / γ particles - ➔ Due to relatively negligible mass of consists of high energy rays. Like X electrons, they are ignored when rays, γ rays have no charge and are calculating the mass of an atom. not affected by an external field. Proton (+) ➔ positively charged particles Atomic Number & Mass Number ➔ charge of proton: 1e, approximately 1.602 x 10-19  1) Superscript denotes mass number (A) and Subscript denotes atomic number (Z) Atomic Number (Z) 2) Mass number is always greater ○ number of protons in the than atomic number. nucleus of each atom of an element. 3) When no subscript is shown, atomic Mass Number (A) number can be deduced from the ○ total number of neutrons and element symbol/name. protons present in the nucleus of an atom of an element. 4) The number of electrons is equal to the number of protons. ** Mass number = Number of protons + Number of neutrons = Atomic number + Number of neutrons ** Basic Laws of Matter Law of Conservation of Mass (John TAKE NOTE: Dalton, English Scientist, 4th 1. Number of neutrons is equal to: Hypothesis) mass number - atomic number ○ Matter can be neither (A - Z) created nor destroyed. 2. Atomic number, number of neutrons, and mass number must be positive whole numbers. Isotopes ➔ atoms that have the same atomic number but different mass numbers. Law of Conservation of Mass ➔ element (X), mass no. (A), and (Antonie Lavoisier, 1743-1794, atomic number (Z) result of combustion experiment) ○ Mass is conserved. Total mass present before and after a chemical reaction is the Examples: same. Law of Definite Proportions (Joseph Proust, French Chemist, 1799) ○ Different samples of the same compound always contain its constituent Atomic Number, Mass Number, & elements in the same Isotopes proportion by mass. ★ How to calculate the number of Law of Multiple Proportions (John protons, neutrons, and electrons Dalton, English Scientist, 3rd using atomic numbers and mass Hypothesis) numbers ○ If 2 elements combine to form more than one  compound, the masses of one Ion is an atom or group of atoms that element that combine with a has a net positive or negative fixed mass of the other charge. element are in ratios of small 2 Types of Ions: Cations & Anions whole numbers. 1. Cation (+) - ion with a net positive charge due to a loss of 1 or more electrons from a neutral atom. 2. Anion (-) - ion with a negative net charge due to an increase in the number of electrons. Ionic Compound - formed from Molecules cations and anions. Examples: Molecule is an aggregate of at least ○ NaCI, CaCO3 , NaOH, 2 atoms in a definite arrangement Na2SO3 , K3PO4 held together by chemical forces/bonds. Monoatomic Ions - contain only 1 May contain atoms of the same atom and are formed by the loss or element or atoms of 2 or more gain of more than 1 electrons. elements joined in a fixed ratio, in Examples: accordance with the law of definite ○ Mg2+, Fe3+, S2-, N3-, Na+, CI- proportions. Polyatomic Ions - ions containing Diatomic Molecule - contains only 2 more than 1 atom, where two or atoms; can contain atoms of different more atoms combine to form an ion elements. with a net positive or net negative Examples: charge. ○ H2 , N2 , O2 Examples: ○ Group 7A Elements ○ OH-, CN-, NH+4 ○ HCI ○ CO Polyatomic Molecule - contains more than 2 atoms; can be combinations of 2 or more different elements. Examples: ○ O2 ○ H2O ○ NH3 Ions  Ionic compounds - A compound that is formed by ionic bonding, which occurs through electron TOPIC 6: FORMULA AND transfer. NOMENCLATURE STEPS IN WRITING THE CHEMICAL FORMULA FOR IONIC COMPOUNDS. Chemical Formula - used to express the composition of molecules and ionic 1. Write the metal ion , followed by compounds in terms of chemical symbols. nonmetal ion with their charges. 2. The overall compound must be 2 Types of chemical formula electrically neutral, decide how many of each ion is needed in order for the positive a.) MOLECULAR and negative charges to cancel each other - Gives the composition of the out. molecule, in terms of the actual 3. Write the symbol and charge of the cation number of atoms present. first and the anion second. - Shows the exact number of atoms of 4. Use a multiplier to make the total charge each element. of the cations and anions equal to each b.) CHEMICAL other. Allotrope - one of two or more 5. Use the multipliers as subscripts. distinct forms of an element. 6. Write the final formula EMPIRICAL FORMULA - Gives the composition of the IONS molecule, in terms of the Ion - an atom or a group of atoms that has a smallest ratio of the number net positive or negative charge of atoms present. Cation (+) - ion with a net positive charge - Tells us which elements are due to the loss of one or more electrons from present and the simplest a neutral atom. whole-number ratio of their Anion (-) - net charge is negative due to an atoms, but not necessarily the increase in the number of electrons. actuarial number of atoms. Monoatomic ions - contain only one atom MOLECULAR MODELS Polyatomic ions - consist of groups of atoms bonded together and have an overall Molecular formula electric charge. - Representation of a molecule - They follow the rules of writing the that uses chemical symbols chemical formula for monoatomic ions, but followed by subscripts if more than one of a polyatomic ion is Structural formula needed to balance the charge, the entire - Two-dimensional model formula must be enclosed in parentheses, showing how atoms are and the subscript is placed outside. bonded to one another. Ball and stick model IONIC VS MOLECULAR (COVALENT) - Three-dimensional model where the atoms are depicted Ionic as color-coded balls. - formed when a metal and a nonmetal Space-filling model combine - Realistic model where atoms - readily lose electrons reacts with an are scaled up in size to fill the element composed of atoms that readily gain space between each other. electrons, transfer of electrons occurs CHEMICAL FORMULA Molecular - formed by a combination of nonmetals. - result when atoms share, rather than 1. Place the name of the first element in the transfer electrons formula first, and the scond element is named by adding “-ide” to the root of the element name. MOLECULES Diatomic molecule 2. Use of Greek prefixes to denote the - Contains only two atoms number of atoms Polyatomic molecule - Containing more than two 3. Prefix “mono-” may be omitted for the atoms first element. NOMENCLATURE 4. For oxides, the ending “a” in the prefix is Organic compounds sometimes omitted. - Contain carbon, usually in combination with elements 5. Exceptions to the use of greek prefixes such as hydrogen, oxygen, are molecular compounds containing nitrogen, and sulfur. hydrogen Inorganic compounds - Group of chemicals that contain no carbon, including ammonia, hydrogen sulfide, all metals, and most elements. 4 CATEGORIES OF INORGANIC COMPOUNDS 1. Ionic compounds 2. Molecular compounds 3. Acid and bases 4. Hydrates NAMING IONIC COMPOUNDS 1. Metal cations take their names from the elements. NAMING ACID AND BASES 2. For binary and ternary compounds, the Acids are substances that yield hydrogen first element named is the metal cation, ions (H+) when dissolves in water followed by nonmetallic anion. Anion is named by adding “-ide” at the end of the Bases are substances that yield hydroxide name of an element. ions (OH-) when dissolved in water. 3. Old nomenclature: transition metals can 1. Formulas for acid contain one or more form more than one type of cation. Use the hydrogen atoms as well as an anionic group. suffix “-ous” to the cation with fewer positive charges and the ending “-ic” to the 2. Anions whose names end in “-ide” from cation with more positive chargers. acids with a “hydro-” prefix and an “-ic” suffix. 4. New nomenclature: stock system uses roman numerals to designate different NAMING OXYACIDS cations while retaining the original name of the cation. (I - one positive charge) Oxoacids are acids that contain hydrogen, oxygen, and another element (central NAMING MOLECULAR COMPOUNDS element)  Calcium Oxide (CaO) - lime 1. The formulas are usually written with the Sodium Tetraborate (Na2B4O7) - borax H first, followed by the central element [(CH3)2O] - acetone and then O. Ascorbic Acid C6H8O6 - vitamin c Carbon Trihydrogen (CH3) - methane Often two or more oxoacids have the same (NH3) - Ammonia central atom but a different number of O (NH4) - ammonium atoms. Starting with the reference for oxoacids whose names all end with “-ic”, AVERAGE ATOMIC MASS use the following rules: - The sun of the masses of its isotopes, each multiplied by its natural abundance. 1. Addition of one O atom to the “-ic” acid: The acid is called “per..ic” acid FORMULA: ∑ atomic mass * % abundance of isotope 2. Removal of one O atom from the “-ic” acid: The acid is called “-ous” acid 3. Removal of two O atoms from the “-ic” acid called “hypo…-ous” acid. NAMING OXOANIONS 1. When all the H ions are removed from the “-ic” acid, the anion’s name ends with “- ate” MOLECULAR MASS 2. When all the H ions are removed from the Molecular Mass or Formula Mass - sum “-ous” acid, the anion’s name ends with “- of the average atomic masses of the atoms in ite” the molecule. 3. The names of anions in which one or more but not all the hydrogen ions have been removed must indicate the number of H ions present. NAMING HYDRATES Hydrates are compounds that have a specific number of water molecules attached MOLE CONCEPT AND AVOGADRO’S to them. NUMBER 1. Follow the general rules in naming MOLE chemical compounds - Special unit of measure used to deal 2. Use prefixes in describing the number of with extremely large numbers. water molecules attached in the compound. - Contains as many entities as the are in exactly 12g of carbon-12 glossary of common chemical names - Number of atom in carbon-12: 6.022 x 1023 Dihydrogen monoxide (H2O) - water - 1 dozen = 12 entities Sodium Chloride (NaCl) - salt - 1 mole = 6.022 x 1023 entities Iron Oxide (Fe2O3) - rust Sodium Bicarbonate (NaCHO3) - baking soda Calcium Carbonate (CaCO3) - chalk/marble  BASIC FORMULA: CATEGORIES Number of MOLES of atoms 6.022 x 1023 Metal - good conductor of heat and atoms = UNIT: ans [element electricity ATOMSNumber = of moles x 6.022 Non-metal - poor conductor of heat and electricity UNIT: (ans) moles of [element Metalloid - has properties that are MOLECULES Number of moles x intermediate between those of metals and nonmetals UNIT: (ans) molecules Note: this formula is the short method we HOW TO READ THE PERIODIC can use for exams, check the ppt for the TABLE full formula. Molar Mass - Mass in grams of one o=mole of a substance. - Unit: g/mol - The molar mass in grams is numerically equal to the atomic mass, molecular mass, and formula mass in amu. GROUP 1: ALKALI METALS Formula: elements are extremely reactive Amu = molar mass = formula mass water-sensitive Amu = g/mol silvery, white, and light have low melting and low boiling points TOPIC 7: PERIODIC TABLE of ELEMENTS PERIODIC TABLE - formed from cations and anions. PERIODS - horizontal rows based on atomic number -same number of electron orbitals GROUP 2: ALKALINE EARTH METALS GROUPS/FAMILIES - vertical columns according to similarities in their chemical second most reactive properties strong reducing agents that donate -same number of valence electrons electrons in chemical reactions good thermal and electrical conductors  low density, low melting point, and a low boiling points POST TRANSITION METALS located in between the transition metals and the metalloids at standard temperature, they are in a solid state of matter tend to have a high density as well as high LANTHANIDES: RARE EARTH conductivity METALS malleable and ductile contain one valence electron in the 5d shell highly reactive and a strong reducing agent in reactions silvery-bright metal and are relatively soft high melting points and high boiling points ACTINIDES: RARE EARTH METALS highly reactive high electropositivity and are radioactive contain paramagnetic pyromorphic and METALLOIDS allotropic properties physically they are very similar to display properties of both metal and lanthanides nonmetals silvery metals that are soft, malleable, and metals are good conductors and nonmetals ductile are poor conductors semiconductors (only conducts electricity at high temp” more brittle than metals but less brittle than nonmetals can be either shiny or dull typically ductile and malleable GROUP 3-11: TRANSITION METALS typically form two or more oxidation states Iow ionization energies and high NONMETALS conductivity low melting and boiling points high melting points, high boiling points, don’t conduct heat or electricity very well and high conductivity tend to have high ionization energies and metallic and malleable electronegativity values  don’t have the shiny “metallic” appearance ATOMIC RADIUS - Express the size of atom - Distance between nuclei of two identical atoms bonded together is measured. Trend - decreases from left to right across a period - small exemptions, such as oxygen radius GROUP 17: HALOGENS being slightly greater than nitrogen radius - increases from top to bottom within a means “salt formers” in greek group. interact with metals to form various salts only periodic family that contains elements in the three states of matter at standard temperature. six halogens and they are located in group 17. highly reactive, highly electronegative, and highly toxic nonmetals. NOBLE METALS inert due to having a complete valence CONCEPTS BEHIND THE TREND shell like nobles gases Period have catalytic tendencies - within a period, protons are added to the very resistant to corrosion, tarnishing, and nucleus as electrons are being added to the oxidation same principal energy level. These electrons soft and ductile are gradually pulled closer to the nucleus because of its increased positive charge. Since the force of attraction between nuclei and electrons increases, the size of atoms decreases. Group - as the atomic number increases down a group, there is again an increase in positive NOBLE GASES nuclear charge. However, there is also an aerogenes increase in the number of occupied principal inert gases energy levels. Higher principal energy levels have a complete valence shell consist of orbitals which are larger in size stable and relatively unreactive than the orbitals from lower energy levels. have low boiling points and low melting points colorless and have no smell PERIODIC TRENDS  lonization Energy energy required to remove the outermost or least bound, electron from a neutral atom of the element quantity of energy that an isolated, gaseous atom in the ground electronic state must absorb to discharge an electron, resulting in a cation Electron Affinity Trend - increases as you move left to right energy change that occurs when a neutral across a period atom gains an electron When energy is released in a chemical reaction or process, that energy is expressed as a negative number. measured in the gaseous state Trend - increases as you move left to right across a period Concept behind the Trend increase (become more negative) from left Period to right across a period Within a period, increasing nuclear charge, decrease (become less negative) from top which results in the outermost electron being to bottom down a group more strongly bound to the nucleus, changes the ionization energy of an atom 1st ionization - require less energy Successive ionization requires more and more energy Period ELECTRON CONFIGURATION The further away an electron is from the nucleus, the easier it is for it to be expelled. Used for: lonization energy is a function of atomic 1. Determining the valency of an element radius, the larger the radius, the smaller the amount of energy required to remove the 2. Predicting the properties of a group of electron from the outermost orbital elements 3. Interpreting atomic spectra Helps us see how electrons are arranged in atomic orbitals for a specific element. Shells - The maximum number of electrons that can be accommodated in a shell is based on the principal quantum number (n). It is represented by the formula 2n2..where 'n' is the shell number. Subshells The subshells into which electrons are distributed are based on the azimuthal quantum number (denoted by 'l'). Quantum number is dependent on the value of the principal quantum number, n. Therefore, when n has a value of 4, four different subshells are possible. When n=4. The subshells correspond to I=0, 1-1, 1-2, and 1-3 and are named the s, p, d, and f subshells, respectively. The maximum number of electrons that can be accommodated by a subshell is given by the formula 2x (21+1) Types of Subshells How to Read the Electron Configuration s subshell - has one orbital that can hold up 1. Always start counting from Hydrogen and to two electrons make a way going from left to right (row after row) to the element you are trying to p subshell - has three orbital that can hold find. up to six electrons 2. For FULL or EXTENDED Electron d subshell - has five orbital that can hold up Configuration: to ten electrons - Count the number of movement you f subshell - has seven orbital that can hold make to identify the number of up to fourteen wo electrons superscript to be used Blocks of Subshells in the Periodic Table 3. For ABBREVIATED or CONDENSED Electron Configuration: Think of the noble s block - first two groups, including helium gas that is in the row before the element you are looking for as a placeholder or the new p block - groups at the right side place to start and then continue counting for the remaining parts. d block - inner transition metals 4. When counting for the configuration of f block - bottom transition metals elements in d block, the coefficient in front is always one less than the row it is in. 5. When counting for the configuration of elements in the f block, the coefficient in front is always two less than the row it is in. EXAMPLES: “SORRY PO NALATE ANG TAGAL KASI NI JJ GAWIN PART NYA”