Chapter 2 - Atoms and Elements

Question 1

What is the law of conservation of mass?

Answer 1

In a chemical reaction, matter is neither created nor destroyed

Question 2

What is the law of definite proportions?

Answer 2

All samples of a given compound, regardless of their source or how they were prepared, have the same proportions as their constituent elements

Sometimes called the law of constant composition; all pure substances contain the same elements in the same proportions

Question 3

What is the law of multiple proportions?

Answer 3

When two elements (call them A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers

Question 4

What is John Dalton’s atomic theory?

Answer 4

1. Each element is composed of tiny, indestructible particles, called atoms
2. All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements
3. Atoms combine in simple, whole-number ratios to form compounds
4. Atoms of one element cannot change into atoms of another element. In a chemical reaction, atoms only change the way they are bound together with other atoms

Question 5

What is radioactivity?

Answer 5

The emission of subatomic particles or high energy electromagnetic radiation by the unstable nuclei of certain atoms

Question 6

What is the nuclear theory?

Answer 6

The theory that most of the atom’s mass and all of its positive charge is contained in a small, dense nucleus

Most of the volume of the atom is empty space, throughout which tiny, negatively charged electrons are dispersed

There are as many negatively charged electrons outside the nucleus as there are positively charged particles (protons) within the nucleus, so the atom is electrically neutral

Question 7

What is the nucleus?

Answer 7

The very small dense core of the atom that contains most of the atom’s mass and all of it’s positive charge; composed of protons and neutrons

Question 8

What are protons?

Answer 8

Positively charged subatomic particles found in the nucleus of an atom

Question 9

What are neutrons?

Answer 9

An electrically neutral subatomic particle found in the nucleus of an atom, with a mass almost equal to that of a proton

Question 10

What is the atomic mass unit?

Answer 10

amu; a unit used to express the masses if atoms and subatomic particles, defined as 1/12 the mass of a carbon atom containing 6 protons and 6 neutrons

The mass of a proton or neutron is approximately 1 amu

Electrons have a mass of 0.00091 x 10^-27 kg or 0.00055 amu

Question 11

What is the atomic number?

Answer 11

The number of protons in an atom; the atomic number defines the element

Given the symbol Z

Question 12

What are isotopes?

Answer 12

Atoms with the same number of protons but with different numbers of neutrons

Question 13

What is natural abundance?

Answer 13

The relative percentage of a particular isotope in a naturally occurring sample with respect to other isotopes of the same element

Each element has its own characteristic natural abundance of isotopes

Question 14

What is the mass number?

Answer 14

The sum of the number of protons and neutrons in an atom

Represented by the symbol A

Question 15

What are ions?

Answer 15

An atom of molecule with a net charge caused by the loss or gain of electrons

Question 16

What are cations?

Answer 16

Positively charged ions

Question 17

What are anions?

Answer 17

Negatively charged ions

Question 18

What is the periodic law?

Answer 18

A law based on the observation that when the elements are arranged in the order of increasing mass, certain sets of properties recur periodically

*To be periodic means to exhibit a repeating pattern

Question 19

How are elements broadly classified?

Answer 19

Metals; lie on the lower left side and middle of the periodic table

Non metals; lie on the upper right side of the periodic table

Metalloids; lie along the zigzag line that divides metals and non metals

Question 20

What are metals?

Answer 20

A member of the class of elements that are generally good conductors of heat and electricity, are malleable, ductile (drawn into wires), lustrous (shiny), and tend to lose electrons during chemical changes;

Chromium, copper, strontium, and lead are typical metals

Question 21

What are non metals?

Answer 21

A member of the class of elements that tend to be poor conductors of heat and electricity, and usually gain electrons during chemical reactions;

Oxygen, carbon, sulfur, bromine, and iodine are non metals

Question 22

What are metalloids?

Answer 22

A member of the class of elements found on the boundary between metals and non metals of the periodic table, with properties intermediate between those of both groups; also called semimetals

Silicon, arsenic, and antimony are metalloids

Question 23

What are semiconductors?

Answer 23

A material with intermediate electrical conductivity that can be changed and controlled

Question 24

What are noble gases?

Answer 24

The group 8A elements; largely unreactive (inert) due to their stable filled p orbitals

Most familiar noble gas is helium; neon, argon, krypton, and xenon are also noble gases

Question 25

What are alkali metals?

Answer 25

Highly reactive metals in the group 1A of the periodic table

Question 26

What are alkaline earth metals?

Answer 26

Fairly reactive metals in the group 2A of the periodic table; calcium, magnesium, strontium, and barium

Question 27

What are the halogens?

Answer 27

Highly reactive non metals in group 7A of the periodic table; chlorine, bromine, iodine, fluorine

Question 28

What are the three general divisions of the periodic table?

Answer 28

1. Main group elements; found in the s and p blocks of the periodic table whose properties tend to be predictable based on their position in the table 2. Transition elements; found in the d block of the periodic table whose properties tend to be less predictable based simply on their position in the table 3. Transition metals; found in the d block of the periodic table whose properties tend to be less predictable based simply on their position in the table

Question 29

What is atomic mass?

Answer 29

The average mass in amu of the atoms of a particular element based on the relative abundance of the various isotopes; numerically equivalent to the mass in grams of one mole of the element

Question 30

What is mass spectrometry?

Answer 30

An experimental method of determining the precise mass and relative abundance of isotopes in a given sample using an instrument called a mass spectrometer that separates particles according to their mass

Question 31

What is a mole?

Answer 31

A unit defined as the amount of material containing 6.0221421 x 10^23 particles (Avogadro's number)

Question 32

What is molar mass?

Answer 32

The mass in grams of one mol of atoms of an element; numerically equivalent to the atomic mass of the element in amu The molar mass of any element is the conversion factor between the mass (g) of that element and the amount (moles) of that element