Chemistry Final

What did ancient Greek philosophers believe about matter?

They viewed matter as being composed of elements or simpler substances.

What were the two models developed to understand matter?

1. Continuous (infinitely divisible) 2. Discontinuous (made up of particles called atoms)

What was Dalton's contribution to atomic theory in the early 1800s?

He proposed that matter was composed of hard, indivisible atoms that joined or dissociated during chemical change.

What discovery did Thomson make about cathode rays in 1897?

He discovered that cathode rays were negatively charged particles known as electrons.

What model did Rutherford develop based on alpha particle experiments?

He developed a solar system model with a small, massive, positively charged nucleus surrounded by moving electrons.

What is the significance of the atomic number?

The atomic number is the number of protons in an atom.

What are isotopes?

Atoms of elements with different numbers of neutrons.

How is the mass of isotopes compared?

The mass of each isotope is compared to carbon-12, which is assigned a mass of exactly 12.00 atomic mass units.

What is atomic weight?

The mass contribution of the isotopes of an element according to their abundance.

How are isotopes identified?

By their mass number (sum of protons and neutrons) and chemical symbol, with the atomic number as a subscript and mass number as a superscript.

What model did Bohr develop for the hydrogen atom?

He developed a model explaining the characteristic line spectra emitted by hydrogen, specifying allowed orbits for electrons.

What happens when an electron jumps from a higher orbit to a lower one in Bohr's model?

It gives up energy in the form of a single photon.

What was De Broglie's proposal regarding electrons?

He proposed that moving particles of matter (electrons) should have wave properties like photons.

What did De Broglie's derived equation show?

It showed that matter waves were only measurable for very small particles such as electrons.

What is the quantum mechanical model of the atom?

It describes the energy state of the electron in terms of quantum numbers based on the wave nature of the electron.

What do quantum numbers define in the quantum mechanical model?

They define the probability of the location of an electron in fuzzy regions of space called orbitals.

What are the horizontal rows and vertical columns in the periodic table called?

Horizontal rows are called periods, and vertical columns are called families.

What do members of a given family in the periodic table have in common?

They have the same outer orbital electron configurations.

Why is electron configuration important?

It is mostly responsible for the chemical properties of an element.

What are elements?

Basic substances that cannot be broken down into anything simpler.

What is an atom?

The smallest unit of an element.

What are compounds?

Combinations of two or more elements that can be broken down into simpler substances.

How are compounds formed?

When atoms are held together by an attractive force called a chemical bond.

What is a molecule?

The smallest unit of a compound or a gaseous element that can exist and still retain the characteristic properties of a substance.

What is a chemical change?

A process that produces new substances with new properties by making or breaking chemical bonds.

What is a chemical reaction?

The process of forming or breaking chemical bonds to create different chemical substances.

What is chemical energy?

The change of internal potential energy during a chemical reaction.

What does a chemical equation represent?

A shorthand way of describing a chemical reaction, showing reactants on the left and products on the right.

What are valence electrons?

Electrons in the outermost orbital of an atom that are involved in chemical bonding.

What is the octet rule?

The tendency of atoms to lose or gain electrons to achieve a noble gas structure of eight electrons in the outer orbital.

What is a chemical bond?

An attractive force that holds atoms together in a compound.

What is an ionic bond?

A bond formed when atoms transfer electrons to become ions, resulting in an electrostatic attraction between oppositely charged ions.

What is a covalent bond?

A bond formed when atoms share electrons.

What is the heat of formation?

The energy released when an ionic compound is formed, equal to the energy required to decompose the compound into its elements.

What does a formula of a compound indicate?

The elements present in a compound and their proportions.

What are covalent compounds?

Molecular compounds composed of electrically neutral groups of atoms bound together by covalent bonds.

What is a single covalent bond?

A bond formed by the sharing of a pair of electrons, with each atom contributing one electron.

What are double and triple bonds?

Double bonds are formed by sharing two pairs of electrons; triple bonds are formed by sharing three pairs of electrons.

What is electronegativity?

The electron-pulling ability of an atom in a bond.

What indicates an ionic bond versus a covalent bond based on electronegativity?

A difference of 1.7 or more indicates an ionic bond; less than 0.5 indicates a covalent bond; between 0.5 and 1.7 indicates a polar covalent bond.

What is a dipole?

A molecule with two poles of charge, resulting from a polar covalent bond.

What is a dipole in chemistry?

A molecule with two poles or centers of charge.

How are ionic and covalent compounds named?

They are named using systematic rules, typically ending with an 'ide' suffix for compounds made of two different elements.

What does the modern systematic naming system for variable-charge ions include?

It states the English name and gives the charge with Roman numerals in parentheses.

What must ionic compounds demonstrate in their formulas?

They must show a balance of charge and be electrically neutral.

What is the crossover technique in chemistry?

An easy way to write formulas that show a balance of charge.

What are covalent compounds?

Molecules of two or more nonmetal atoms held together by covalent bonds.

How are covalent compounds named?

Using Greek prefixes to indicate the number of atoms present.

What is the difference between an empirical formula and a molecular formula?

An empirical formula identifies the simplest whole number ratio of atoms, while a molecular formula identifies the actual number of atoms in a molecule.

What is formula weight?

The sum of the atomic weights of all the atoms in a chemical formula.

What is molecular weight?

The formula weight of a molecular substance.

How can formula weight be used in chemistry?

It can determine the mass percentage of elements in a compound.

What is a balanced chemical equation?

A chemical equation with the same number of each kind of atom on both sides, in accordance with the law of conservation of mass.

What is the law of conservation of mass?

It states that atoms are neither created nor destroyed in a chemical reaction.

How are chemical equations balanced?

By placing coefficients in front of chemical formulas, while subscripts may not be changed.

What are oxidation-reduction reactions?

Reactions where shifts of electrons occur, involving oxidation and reduction processes.

What is oxidation in a chemical reaction?

The process of losing electrons.

What is reduction in a chemical reaction?

The process of gaining electrons.

What are oxidizing agents?

Substances that take electrons from other substances.

What are reducing agents?

Substances that supply electrons.

What are the four classifications of chemical reactions?

1) Combination, 2) Decomposition, 3) Replacement, 4) Ion exchange.

Which of the four classifications of chemical reactions are redox reactions?

Combination, decomposition, and replacement reactions are redox reactions; ion exchange is not.

What is Avogadro's number?

The number of atoms in exactly 12.00 g of C-12, valued at 6.02 × 10^23.

What is a mole in chemistry?

A substance that contains Avogadro's number of atoms, ions, molecules, or any chemical unit.

What is the gram-atomic weight of an element?

The mass in grams that is numerically equal to its atomic weight.

What is the gram-formula weight of a compound?

The mass in grams that is numerically equal to the formula weight of the compound.

What is the gram-molecular weight?

The gram-formula weight of a molecular compound.

How can the mole concept be applied in chemical reactions?

It can be used with mass ratios for calculations about the quantities of reactants and products.

What is the composition of a water molecule?

A water molecule consists of two hydrogen atoms and one oxygen atom.

Why is water considered a polar molecule?

Oxygen has more positive protons than hydrogen, causing electrons to spend more time around oxygen, creating centers of negative and positive charge.

What is a hydrogen bond?

An attractive force between the negative center of one polar water molecule and the positive center of another.

What effects do hydrogen bonds have on water?

They account for the decreased density of ice, high heat of fusion, and high heat of vaporization.

What is a solution?

A homogeneous mixture of ions or molecules of two or more substances.

What is the difference between a solvent and a solute?

The solvent is the substance present in the larger amount, while the solute is dissolved in the solvent.

What are miscible and immiscible fluids?

Miscible fluids mix in any proportion, while immiscible fluids do not mix.

What is the general rule for solubility?

Like dissolves like; polar substances dissolve in polar solvents.

What is concentration in the context of solutions?

The relative amount of solute in a solvent.

How can concentrations be measured?

In parts per million (ppm), percent by volume, percent by weight, and salinity.

What is a saturated solution?

A solution with equilibrium between solute dissolving and solute coming out of solution.

What is solubility?

The concentration of a saturated solution at a particular temperature.

What are electrolytes?

Water solutions that carry an electric current.

What distinguishes strong acids from weak acids?

Strong acids ionize completely in water, while weak acids are only partially ionized.

What is the pH scale?

A scale measuring the strength of acids and bases based on hydronium ion concentration.

What does a pH of 7 indicate?

It indicates a neutral solution.

What is a salt in chemistry?

Any ionic compound except those with hydroxide or oxide ions.

How does hard water affect soap lathering?

Hard water, containing magnesium or calcium, makes it difficult to create soap lather.

How can hard water be softened?

By removing the magnesium and calcium ions.