CHEM Chapter 2 Study Help

What are atoms?

the smallest units of an element

How many atoms make up an element?

1

A compound contains…

the atoms of 2 or more different elements

Dalton’s Atomic Theory is that…

atoms don’t change identity in chemical reactions only how they’re joined does

What is the law of constant composition?

all samples of a substance contain the same elements in the same proportion by mass

What is the law of multiple proportions?

same elements make more than one compound → the mass of one combined with the fixed mass of the other are in a ratio of small whole numbers

What is the law of conservation of mass?

mass does not change (or can’t be detected to change) when a chemical reaction occurs

Name the subatomic particles!

electrons, protons & neutrons

Electrons are…

negatively charged

Protons are…

positively charged

Neutrons…

have no charge

What is the relative charge & mass of an electron?

relative charge: 1-

relative mass: 0

What is the relative charge & mass of a proton?

relative charge: 1+

relative mass: 1

What is the relative charge & mass of a neutron?

relative charge: 0

relative mass: 1

What does the nucleus of an atom contain?

the mass & a high positive charge (protons)

What does the “empty” space of an atom contain?

electrons

The charge of a proton is __ to the charge of an electron

=

Protons & neutrons make up about ____ of the nuclear mass respectively.

half

The atomic number is the number of ______ in the nucleus of the atom

protons

What determines the identity of an element?

# of protons

What symbol represents the atomic number?

Z

The mass number is the sum of the # of _____ + _____ in the nucleus.

protons; neutrons

What symbol represents the mass number?

A

Isotopes are…

atoms of an element that have nuclei containing different #’s of neutrons

What symbol is used to identify isotopes? (hint: this is not a formula, I just don’t have any other way to position it TT)

(A/Z)X

What does the X represent when used to identify isotopes?

the letter(s) symbol for the element (ex. H, He)

Z is often omitted (not included) from the symbol for isotopes. (T/F)

True

Ions are…

the resulting charged particles that come from atoms gaining or losing electrons

Cations have a ______ charge & form when an atom _____ one or more electrons.

positive; loses

Anions have a ______ charge & form when an atom _____ one or more electrons.

negative; gains

If an element has ions, where would the symbol for that be located?

in superscript following the element, represented as a number followed by a charge (+/-)

What happened to this calcium atom: Ca²⁺?

it lost 2 electrons

What happened to this chlorine atom: Cl^-?

it gained 1 electron

How do you find the charge for an ion?

subtracting the electrons from the protons (p+ - e-)

What symbol represents the atomic mass unit?

u

The atomic mass unit is….

1/12 the mass of one ¹²C atom; the mass of a single proton/neutron

What is the atomic mass unit of one ¹²C atom?

12 u

What is the atomic mass unit of one ²⁴Mg atom?

about 24 u

What is the atomic mass unit of one ⁴He atom?

4 u

When does the atomic mass unit become the mass number?

when rounded to a whole #

A ____________ measures the masses & abundances of isotopes.

mass spectrometer

Is the relative abundance of an element’s abundance consistent throughout nature?

Yes

Isotopic mass is…

the mass of a particular isotope of an element

To calculate the atomic mass, find the…

weighted average mass of the element’s natural isotopes

The formula for atomic mass is…

[(percentage of isotope A) x (isotopic mass A)] + (percentage of isotope B) x (isotopic mass B)] + …..

_______ & _______ both separately proposed the periodic table.

Dmitri Mendeleev; Lothar Meyer

On the periodic table elements with similar properties are arranged in the same ______.

column

The horizontal row on the periodic table is referred to as the…

period

The vertical column on the periodic table is referred to as the…

group or family

A metal is…

an element that’s shiny & conducts electricity well

Where are metal elements located on the periodic table?

the center & left

A nonmetal is…

an element that’s usually a nonconductor (doesn’t conduct electricity)

Where are nonmetal elements located on the periodic table?

the top right

A metalloid is…

an element that has both metal & nonmetal properties

Where are metalloid elements located on the periodic table?

the staircase separating metals & nonmetals

What groups are representative elements in?

A groups

What groups are transition metals in?

B groups

What groups are inner transition metals in?

lanthanides & actinides (2 groups at the bottom of the periodic table)

Alkali metals are _______ in group ____

soft, reactive metals; 1A

Alkaline earth metals are _______ in group ____

; 2A

Halogens are _______ in group ____

reactive nonmetals; 7A

Noble gases are _______ in group ____

stable, largely inert (nonreactive) gases; 8A

A molecule is…

a combo of atoms (usually nonmetals) joined so strongly they act as 1 particle

How many atoms do diatomic molecules have?

2

Homonuclear diatomics contain _____

2 of the same atom

Heteronuclear diatomics contain _____

2 different atoms

If all atoms are the same in a molecule the substance is a(n) _____

element

If 2 or more elements form a molecule it is a(n) _____

molecular compound

_________ form molecular compounds.

nonmetals

A molecular formula gives the…

# of every type of atom in a molecule

A structural formula shows…

how the atoms connect in the molecule

structural formula

molecular formula

What is the molecular mass?

the sum of the atomic masses of all atoms represented in the molecular formula

How is molecular mass expressed?

atomic mass units (u)

What are the 7 homonuclear molecular compounds?

oxygen, nitrogen, fluorine, iodine, chlorine, bromine, hydrogen

Ionic compounds consist of a _______ _______ and a ______ ______

metal cation (+); nonmetal anion (-)

What formula is used for ionic compounds?

the empirical formula

All ionic compounds are initially ______.

neutral

Which groups on the periodic table have cations?

1A, 2A, some of 3B, and Aluminum in 3A

Which groups on the periodic table have anions?

7A, 6A, and Nitrogen in 5A

What charge does group 1A have?

1+

What charge does group 2A have?

2+

What charge does group 3A & 3B have?

3+

What charge does group 7A have?

1-

What charge does group 6A have?

2-

What charge does group 5A (Nitrogen) have?

3-

A polyatomic ion is…

a group of atoms with net charge & behave as a single particle

Show me ammonium.

NH₄⁺

Show me nitrate.

NO₃^-

Show me carbonate.

CO₃^2-

Show me phosphate.

PO₄^2-

Show me sulfate.

SO₄^2-

Show me sulfite.

SO₃^2-

Show me hydroxide.

OH^-

Chemical nomenclature is…

the organized system for naming compounds

For ionic compounds: the name of the ______ comes first, followed by the name of the _____

cation; anion

For ionic compounds: the ending of the element name for the ______ is changed to ______

anion; -ide

What shows the charge for metals that have more than one cation (usually transition metals)?

roman numerals in parentheses

What polyatomic ion represents ammonium?

NH₄⁺