Subatomic Structure and Atomic Models

An atom is the smallest unit of a chemical element, containing a nucleus with protons and neutrons, surrounded by electrons. A molecule is formed when two or more atoms bond chemically, sharing electrons to create a stable structure.

Valence electrons are the electrons in the outermost shell of an atom. They determine the atom's reactivity, as atoms strive to gain or lose valence electrons to achieve a stable configuration. Lewis dot structures visually represent the valence electrons as dots surrounding the chemical symbol of an element, indicating its bonding potential.

The Bohr model depicts the atom as a central nucleus surrounded by electrons orbiting in specific energy levels or shells. It was significant in introducing the quantized nature of electron energy levels and provided a visual representation of atomic structure, although it has been since refined by more complex models.

<p>The three main types of mixtures are suspensions, colloids, and solutions. Suspensions are heterogeneous mixtures where particles settle out over time, like sand in water. Colloids are heterogeneous mixtures with particles that are dispersed throughout the medium, like milk. Solutions are homogeneous mixtures where particles are evenly distributed, like saltwater.</p> Signup and view all the answers

<p>The atomic number is the number of protons in an atom's nucleus. It is unique to each element and determines its identity. Since atoms are electrically neutral, the number of electrons is equal to the number of protons.</p> Signup and view all the answers

<p>Protons reside in the nucleus and have a positive charge (+1). Neutrons are also located in the nucleus and have no charge (neutral). Electrons orbit the nucleus in shells and have a negative charge (-1). Protons and neutrons contribute to the atom's mass, while the balance of protons and electrons determines the overall charge (usually neutral).</p> Signup and view all the answers

<p>To find the number of neutrons, subtract the atomic number (number of protons) from the atomic mass (average mass of all atoms of that element). For example, carbon has an atomic number of 6 and an atomic mass of 12. Therefore, carbon has 6 neutrons (12 - 6 = 6).</p> Signup and view all the answers

<p>An element is a pure substance that consists of only one type of atom, like gold (Au) or oxygen (O). A compound is formed when two or more different elements chemically combine in a fixed ratio, like water (H2O) or salt (NaCl). Elements cannot be broken down further by chemical means, while compounds can be broken down into their constituent elements through chemical reactions.</p> Signup and view all the answers

<p>The atomic size increases as you move down a column.</p> Signup and view all the answers

<p>Noble gases are non-reactive because they have a full valence shell, making them stable.</p> Signup and view all the answers

<p>Subscripts in chemical formulas indicate the number of atoms of an element in a compound.</p> Signup and view all the answers

<p>Ionic bonding involves the transfer of electrons, while covalent bonding involves the sharing of electron pairs between atoms.</p> Signup and view all the answers

<p>Ionization energy increases as you move up and to the right across the periodic table.</p> Signup and view all the answers

<p>Metals are good conductors of heat and electricity, shiny, malleable, and ductile.</p> Signup and view all the answers

<p>Reactivity increases towards the lower left and upper right corners of the periodic table.</p> Signup and view all the answers

<p>Nonmetals are mostly gaseous at room temperature and are generally brittle.</p> Signup and view all the answers

<p>Valence electrons are the electrons in the outermost shell of an atom. They are involved in chemical bonding and determine the reactivity of an atom. Atoms with full outer shells (8 valence electrons) are considered stable and less likely to react because they have no need to gain or lose electrons. Atoms with incomplete outer shells tend to be more reactive because they will either gain or lose electrons to achieve a full outer shell.</p> Signup and view all the answers

<p>An element is a pure substance made up of only one type of atom. For example, gold (Au) is an element. A compound is a pure substance formed when two or more different elements combine chemically in a fixed ratio. For instance, water (H2O) is a compound, formed by the chemical combination of hydrogen and oxygen.</p> Signup and view all the answers

<p>To find the number of neutrons in an atom, subtract the atomic number from the atomic mass. For example, carbon has an atomic number of 6 and an atomic mass of 12. Therefore, carbon has 6 neutrons (12 - 6 = 6).</p> Signup and view all the answers

<p>Atomic mass is the average mass of an atom of an element, taking into account the different isotopes of that element. It's typically represented on the periodic table as a decimal number below the element's symbol. The atomic number is the number of protons in an atom's nucleus, which defines the atom's identity. It's represented as a whole number above the element's symbol.</p> Signup and view all the answers

<p>The Bohr model depicts the atom as a nucleus with protons and neutrons, surrounded by electrons orbiting in specific energy levels or 'shells'. It helped explain the line spectra of atoms and the quantization of energy levels. However, it was limited in its ability to explain the complex behavior of electrons and their interactions with each other. It doesn't account for electron spin or the shapes of electron orbitals.</p> Signup and view all the answers

<p>Noble gases are considered unreactive because they have a full outer shell of valence electrons, making them very stable. They have no tendency to gain or lose electrons to achieve a stable electron configuration. This makes them inert and less likely to participate in chemical reactions.</p> Signup and view all the answers

<p>A Lewis dot structure is a diagram that represents the valence electrons of an atom by using dots around the element's chemical symbol. Each dot represents a valence electron. For example, the Lewis dot structure of oxygen (O) would have the chemical symbol 'O' surrounded by six dots, representing the six valence electrons of oxygen.</p> Signup and view all the answers

<p>A mixture is a combination of two or more substances that are not chemically bonded. Mixtures can be separated by physical means, whereas compounds require chemical reactions for separation. The three main types of mixtures are:</p> <ul> <li>Suspensions: heterogeneous mixtures with particles that settle out over time. Example: sand in water.</li> <li>Colloids: heterogeneous mixtures with particles that don't settle out but scatter light. Example: milk.</li> <li>Solutions: homogeneous mixtures with particles dissolved evenly throughout. Example: saltwater.</li> </ul> Signup and view all the answers

<p>Atomic size decreases as you move from left to right across a row because the increasing positive charge in the nucleus attracts the electrons more strongly.</p> Signup and view all the answers

<p>Chemical symbols represent elements, while subscripts indicate the number of atoms of each element in a compound, such as in H₂O where '2' indicates two hydrogen atoms.</p> Signup and view all the answers

<p>Ionic bonding occurs when one atom gives up an electron to another atom, resulting in a positive ion and a negative ion that are attracted to each other, forming a stable compound.</p> Signup and view all the answers

<p>Noble gases have full valence shells, meaning they do not need to gain or lose electrons to achieve stability, making them non-reactive.</p> Signup and view all the answers

<p>In ionic bonds, electrons are transferred from one atom to another, while in covalent bonds, electrons are shared between atoms.</p> Signup and view all the answers

<p>Ionization energy increases as you move from left to right across a period and from bottom to top in a group, illustrating that atoms become harder to ionize.</p> Signup and view all the answers

<p>Nonmetals in the upper right corner of the periodic table are generally more reactive than those in the bottom left.</p> Signup and view all the answers

<p>Metals are good conductors of heat and electricity, with a shiny appearance and malleability, while nonmetals are generally poor conductors, brittle, and mostly gaseous at room temperature.</p> Signup and view all the answers

The measure of the size of an atom; increases down and left in the periodic table.

Elements in the lower left and upper right corners are most reactive, except noble gases.

Gases with full valence shells; non-reactive and found at the far right of the periodic table.

Metals are good conductors, luster, malleable; Nonmetals are gases, brittle, poor conductors.

Represents elements and compounds using symbols and subscripts.

Atoms transfer electrons to achieve neutrality, forming a compound.

Atoms share pairs of electrons to stabilize electron configuration.

The energy needed to remove an electron from an atom; increases up and to the right.

Positively charged particles located in the nucleus of an atom.

Neutral particles found in the nucleus; no charge.

Negatively charged particles that orbit around the nucleus of an atom.

Center of the atom that contains protons and neutrons.

Model showing the nucleus with orbitals containing electrons depicted by dots.

Chemical symbol surrounded by dots indicating valence electrons.

Pure substances made of identical atoms, like carbon or gold.

Variable combination of two or more pure substances, including solutions.

Atomic size increases as you move down and to the left on the periodic table.

Noble gases are completely non-reactive due to having a full valence shell.

Metals are good conductors, have luster, and are malleable and ductile.

Nonmetals are mostly gases at room temperature and are brittle and poor conductors.

Ionic bonds form when atoms give/receive electrons to achieve a stable charge.

Covalent bonds occur when atoms share pairs of electrons to stabilize their configuration.

Ionization energy increases as you move up and to the right on the periodic table.

The number of protons in an atom, found at the top of the periodic table box.

The weighted average mass of an atom's isotopes, located at the bottom of the periodic table box.

Electrons in the outermost shell of an atom that determine its chemical reactivity.

Pure substances made of two or more different elements in fixed ratios, with different properties from elements.

The particles that make up an atom: protons, neutrons, and electrons.

Atoms are the smallest unit of matter; molecules are groups of atoms bonded together.

To visually represent valence electrons around the chemical symbol of an atom.

Regions around the nucleus where electrons are likely to be found.