Science 1st Sem Reviewer PDF

SCIENCE 1ST SEM REVIEWER Pointers Particle Nature of Mature: Elements, Compounds, and Mixtures; Atoms and Molecules Atomic Structure: Protons, Neutrons, Electrons (Isotopes and Ions) Periodic Table of Elements: Development of the Atomic Theory; Arrangement of Elements; Reactive...

SCIENCE 1ST SEM REVIEWER Pointers Particle Nature of Mature: Elements, Compounds, and Mixtures; Atoms and Molecules Atomic Structure: Protons, Neutrons, Electrons (Isotopes and Ions) Periodic Table of Elements: Development of the Atomic Theory; Arrangement of Elements; Reactive and Nonreactive Metals Quantum Mechanical Model (Electron Configuration) PARTICLE NATURE OF MATTER Matter: Anything that HAS MASS and OCCUPIES SPACE  Properties of Matter ★ Physical properties ○ Determined WITHOUT changing the identity of a substance ○ Has 2 types Extensive physical properties: the AMOUNT of substance Ex. mass, volume, length, shape Intensive physical properties: does NOT depend on the amount Ex. color, melting/boiling point, density ★ Chemical properties ○ CHANGES THE IDENTITY of a substance ○ How the substance REACTS to the presence of: air, acid, base, water, and OTHER CHEMICALS Particles of Matter ★ Atoms is the basic unit of matter and the smallest unit of an element. ★ Elements are made up of tiny particles called atoms that are identical and have the same mass, size, and properties. ★ Molecules is a combination of two or more atoms, an aggregate of at least two atoms. ★ Compounds are composed of atoms of more than one element Laws Governing the Particle Nature of Matter ★ Law of Chemical Combination ○ Empirical laws that govern the CHEMICAL CHANGES ★ Law of Definitive Proportions ○ The composition of a substance is the same REGARDLESS of where it is found or how it’s made ★ Law of Conservation of Mass ○ Matter can neither be CREATED OR DESTROYED, but only TRANSFORMED ★ Law of Multiple Proportions ○ The ratios are FIXED, whole numbers  ○ THERE ARE NO DECIMAL ATOMS Macroscopic level: Visible to the naked eye Microscopic level: Requires an INSTRUMENT to be seen ★ Atoms, molecules Submicroscopic level: can only be identified by knowing how it BEHAVES ★ Solid, liquid, gas Physical and Chemical Changes in Matter ★ Matter is capable of undergoing changes ★ Are classified as either physical or chemical ○ Physical change: the material is STRUCTURALLY THE SAME before and after the change Ex. melting, shedding, boiling, chopping Extensive physical properties ○ Chemical change: there is a CHANGE IN THE CHEMICAL COMPOSITION; often not reversible Ex. combustion, rotting, rusting, digestion Change in temperature/formation of gas or precipitation/color/odor Forms a NEW SUBSTANCE Density ★ Mass per unit of volume ○ Mass (g)/Volume (cm^3) ★ Helps in determining unknown substances because it’s CONSTANT ★ Does not depend on the size or mass of a substance Reactive metals: Lose electrons easily Nonreactive metals: Don’t lose electrons easily Metals ★ Majority of the elements in the periodic table ★ Naturally existing, plentiful ★ Good conductors of electricity ★ Malleable (can be hammered) Nonmetals ★ Usually gas or a brittle solid ★ Can be easily crushed ★ Poor conductors of electricity ★ Not malleable but sometimes transparent Metalloids ★ In between metals and nonmetals ★ Physically are like nonmentals ★ Only some can conduct electricity ★ Are used in electronic devices Periodic Trends ★ Atomic Radius ○ Measure of the size of an atom, usually from the center of the nucleus to the outermost electrons ○ Generally DECREASES from left to right across a period and INCREASES down a group. Francium - biggest atomic radius | Helium - smallest atomic radius ★ Ionic Radius ○ Size of a cation or anion ○ Generally DECREASES across a period, INCREASES down a group ★ Ionization Energy ○ Amount of energy a gaseous atom absorbs to remove its outermost electrons ○ INCREASES across a period and DECREASES down a group ★ Electron Affinity ○ Measure of the energy change that occurs when a gaseous atom gains an electron ○ Generally INCREASES across a period and down a group ★ Electronegativity  ○ Amount of energy a gaseous atom absorbs to remove its outer electrons ○ Increases across a period and decreases down a group ○ Tendency of an atom to attract a shared pair of electrons towards itself in a chemical bond Metallic and Nonmetallic Characters ★ Metallic Character/Electropositivity: Tendency of an element to lose electrons to form a cation ★ Nonmetallic Character/Electronegativity: Tendency of an element to gain electrons to form an anion ★ Across a period, METALLIC characters DECREASE from left to right and down a group, METALLIC characters INCREASE. ★ Across a period, NON METALLIC characters INCREASE from left to right and down a group, NON METALLIC characters DECREASE. ATOMIC STRUCTURE, SUBATOMIC PARTICLES, ISOTOPES AND IONS Atomic Structure ★ Atoms: basic unit of matter ★ Has evolved over time 1803: John Dalton ★ Solid sphere model ★ All matter is composed of small particles called atoms ○ Atoms CANNOT be subdivided, created, or destroyed ○ Atoms of THE SAME ELEMENT have similar properties ○ Atoms of DIFFERENT ELEMENTS have different properties ○ Atoms of different elements can FORM COMPOUNDS ★ Comes from the Greek word “atomos” which means “indivisible” 1904: JJ Thomson ★ Plum Pudding Model ★ Cathode - Ray Tube experiment ★ Electrons are scattered throughout the positive atom ○ Meaning the atom is naturally neutrally charged  ○ Similar to the bits of fruit in a plum pudding 1911: Ernest Rutherford ★ Nuclear model ★ Alpha - particle scattering experiment ★ An atom’s mass is focused on its center: the nucleus ○ Positively charged core at the center ○ Electrons are located OUTSIDE ○ The rest of the atom is mostly empty space 1913: Niels Bohr ★ Planetary model ★ Modelled after Rutherford’s model ★ The electrons ORBIT it instead ★ The energy of an orbit is related to its core ○ When gaining: farther away ○ When losing: closer to the nucleus ★ The innermost orbit can hold up to 2 electrons only 1926: Erwin Schrodinger ★ Quantum model ★ Most accurate to date ★ Electrons do not move in panthers, but in WAVES (clouds) around the nucleus ○ It is impossible to know where electrons are ○ ORBITALS: “clouds of probability”, areas where we are most likely to find electrons ○ Are nearer to the nucleus Because OPPOSITE CHARGES ATTRACT Protons, Neutrons, Electrons ★ Subatomic particles ★ Compose atoms ★ Has 3 kinds: ○ Protons Positive charge Found in the nucleus of an atom  Determines an atom’s ATOMIC NUMBER Protos = “primary one” ○ Neutrons No charge Found in the nucleus along with the protons Composes the atomic weight of an atom (with the amount of protons) ○ Electrons Negative charge Lightest subatomic particle Found ORBITING THE NUCLEUS NOTE: The mass of the protons and electrons DON’T match the mass of the atom, hence the discovery of the NEUTRONS Isotopes and Ions ★ Isotopes ○ Atoms with the SAME ATOMIC NUMBERS but DIFFERENT ATOMIC MASSES ○ ie. Same amount of protons, but different amounts of neutrons ★ Ions ○ When there is a IMBALANCE OF CHARGES in an atom ○ Atoms are NATURALLY NEUTRAL, with even amounts of protons and electrons ○ When they aren’t they’re either: CATION (too many protons) ANION (too many electrons) REMEMBER: Isotopes involve NEUTRONS, Ions involve ELECTRONS THE PERIODIC TABLE OF ELEMENTS IUPAC ★ International Union of Pure and Applied Chemistry  1786: Antoine Laurent Lavoisier ★ Arranged the elements into groups of simple substances that don’t decompose ★ Made a list of 33 elements ★ Were classified between metals and nonmetals ○ Back then they considered light and heat as elements rather than a form of energy ○ Didn’t include the STATES OF ELEMENTS which made it difficult to understand 1808: John Dalton ★ Wrote a book called “A New System of Chemical Philosophy” ○ Contained a table of relative ATOMIC MASSES Had accurate values, but was updated over time ○ Didn’t include the differences of elements of and compounds ★ Introduced atomic masses (protons and neutrons) 1817: John Wolfgang Dobereiner ★ Concluded that certain elements have similar properties ★ Created the “Dobereiner’s Trials” 1828: Jacob Berzelins ★ Published a table that lists the atomic weights of 54 elements ○ Included/introduced SYMBOLS (in alphabetical order) ○ Only a LIST in symbols (no weights) 1829: John Wolfgang Dobereiner ★ After discovering the halogen triad, he proposed that similar elements can be GROUPED into triads (sets of 3) ○ Based on their chemical properties The midde’s atomic weight should be the average of the other two 1862: Alexander-Emile Beguyer de Chancourtois ★ Arranged the elements by INCREASING ATOMIC MASSES ○ Discovered that elements with similar properties were positioned along the SAME VERTICAL LINE 1865: John Newlands  ★ Proposed another way to organize the 62 elements ○ First 20 were arranged by increasing mass, recurred at periodic intervals ★ Law of Octaves 1870: John Lothar Meyer ★ Elements with the same physical and chemical properties occupied the same positions ON THE CURVE ○ Periodic trends 1869: Dmitri Wanovien Mendeleev ★ Published his first diagram in the article: “The Correlation of Properties with the Atomic Weight of Elements” ★ Arranged them in groups with intervals and atomic weights ○ Left gaps for the elements are were yet to be discovered, which made it more accurate ★ Most famous scientist to be credited for the periodic table ★ Didn’t include THE ATOMIC NUMBER 1911: Henry Mosey ★ Said that is was the CHARGE OF THE NUCLEUS (the protons) that determined each element from each other ○ Protons and neutrons = atomic mass ○ Protons = atomic number Periodic Classification ★ Columns: Groups ○ 18 groups ○ Elements in the same groups have SIMILAR PROPERTIES ★ Rows: Periods ○ 7 periods ○ Corresponds to the HIGHEST ENERGY LEVEL Highest energy level: 7 (farthest from the nucleus) ○ Elements on the same period have different properties (because they’re already grouped) QUANTUM MECHANICAL MODEL  ★ Erwin Schrodinger ○ Developed an equation that treated an electron as a wave This developed the possibility of ORBITALS and the QUANTUM MECHANICAL MODEL Quantum Mechanical Model ★ Electrons are in a 3D region around the nucleus called ATOMIC ORBITALS ○ Instead of being in a circular orbit ★ Atomic orbitals predict the location of electrons ○ Fuzzy cloud; it’s denser if there are more electrons ○ 4 types of orbitals: s, p, d, f Refers to the REGION OF PROBABILITY 95% probability Can also be referred to as “BLOCKS” 3D region Denoted with letters and numbers like 1s, 2b, 3d, and 4f The numbers describe the ENERGY LEVELS The letters denote the SHAPE of the orbit They can only hold up to 2 electrons because of their SPIN NOTE: The more electrons, the BIGGER the atom S - orbital ★ Spherical shape ★ Equal probability of finding electrons on all sides ★ 1 subshell = 1 orbital (but two electrons) P - orbital ★ Looks like 2 balloons, dumb shell shape ★ Electrons can be found in the lobes ★ 1 subshell = 3 orbitals D - orbital ★ 1 subshell = 5 orbitals  F - orbital ★ Double dumb shell shape ★ 1 subshell = 7 orbitals Electron Configuration ★ Describes the POSITION of the electrons ★ Distributes electrons per orbital ★ Shows the number of electrons in each atom’s energy level ★ Follows a standard notation ○ ★ Has several uses ○ Determines the valency of an element (how well it can combine with other elements/chemical bounds (may need to double check)) ○ Predicting properties of a group of elements Similar electron configuration = Similar properties Most of the time ○ Determining the atomic spectra The spectrum of electromagnetic radiation emitted or absorbed by an atom (per energy level) Laws about Electron Configuration ★ Aufbau Principle ○ Electrons will occupy the orbitals with LOWER ENERGY LEVELS FIRST before moving on to the higher energy levels ○ Electrons are filled like; 1s, 2s, 2p, 3s, 3p etc. ★ Pauli Exclusion Principle ○ In a maximum of 2 electrons, they need to have OPPOSITE SIGNS So that it has stable configuration (like charges repel)  ★ Hund’s Rule ○ Describes the ORDER IN WHICH ELECTRONS ARE FILLED in all the orbitals belonging to a subshell You have to start at the first orbital and first energy level: 1s Fill with UPWARD ELECTRONS FIRST (distribute throughout all the orbits first before filling them up with the downward electron) QUESTIONS ★ Does having the same electron configuration mean it’s the same element/atom being described? ○ No. It just means that two atoms have the same distribution of electrons and (sometimes) similar properties. ★ Why is s the first to be used when distributing electrons? ○ Because s can hold 2 electrons, so there’s no need to distribute them to the other orbitals ★ Why don’t we have d and f orbital in the first energy level? ○ Because the amount of electrons they can hold doesn’t match the energy levels of 1 and 2 ○ You don’t have to distribute to them because you already have the s and p orbital