Chem Exam 2

What is an atom?

The smallest particle of an element; the building block of matter

What are the three subatomic particles?

Protons, neutrons, and electrons

What is the charge and location of a proton?

+1 charge; located in the nucleus.

What is the charge and location of a neutron?

Neutral (0); located in the nucleus.

What is the charge and location of an electron?

−1 charge; located in the electron cloud around the nucleus.

What is atomic number?

The number of protons in the nucleus. It identifies the element

What is mass number?

The number of protons + neutrons in the nucleus

How do you calculate the number of neutrons?

Mass number − atomic number

What is atomic mass?

The weighted average mass of an element's isotopes.

What is the difference between atomic mass and mass number?

Mass number = protons + neutrons in one isotope. Atomic mass = weighted isotope average.

What are isotopes?

Atoms with the same atomic number but different mass numbers

What causes isotopes to differ?

They have different numbers of neutrons.

How do you calculate average atomic mass?

Multiply each isotope's mass × decimal abundance, then add the products.

How is the periodic table organized?

In order of increasing atomic number.

What are groups?

Vertical (up and down) columns on the periodic table.

What are periods?

Horizontal rows on the periodic table.

What are Group 1A elements called?

Alkali metals

What are Group 2A elements called?

Alkaline earth metals

What are Group 7A elements called?

Halogens

What are Group 8A elements called?

Noble gases

Where are metals found?

On the left and middle of the periodic table

Where are nonmetals founds?

On the right side of the periodic table

Where are metalloids found?

Along the boundary separating metals and nonmetals

What are valence electrons?

Electrons in the highest occupied energy level

Why are valence electrons important?

They are responsible for forming chemical bonds

For main-group elements, what does the group number tell you?

The number of valence electrons

For main group elements, what does the period number tell you?

The valence shell energy level

How many valence electrons does Group 1 have?

1

How many valence electrons does Group 2 have?

2

How many valence electrons does Group 13 have?

3

How many valence electrons does Group 14 have?

4

What color is group 8A?

red

What color is group 7A?

orange

What color is group 1A?

dark people

How many valence electrons does Group 15 have?

5

What is the IUPAC name for this alkane?

3, 4 dimethylhexane

True or false: When naming an alkane, the main chain is the longest continuous carbon chain regardless of bends.

True

True or false: The boiling points of normal hydrocarbons are higher than those of branched hydrocarbons of similar molecular weight because the London-dispersion forces between normal hydrocarbons are greater than those between branched hydrocarbons.

True

Which of these hydrocarbons could not be a cycloalkane?

C₆H₁₄

Give the IUPAC name of the following molecule:

2,2-dimethylbutane

Give the IUPAC name of the following molecule:

1,2-dimethylcyclohexane

What is the condensed structure for an alkane with four carbon atoms?

CH₃CH₂CH₂CH₃

What is the name for a four-carbon continuous-chain alkane?

butane

True or False: Hydrogen sulfide (H₂S) is a covalent compound

True

The name of PCl₃ is __________.

phosphorous trichloride

Which of the following compounds exhibits dipole-dipole intermolecular forces?

CH₃-O-CH₃

What is the electron geometry of a molecule that has two bonding groups and two non-bonding groups around the central atom?

Tetrahedral

Identify the following compound as covalent or ionic.


potassium oxide

Ionic

Identify the following compound as covalent or ionic.


sodium fluoride

Ionic

If the electronegativity difference between elements X and Y is 2.1, the bond between the two elements is…?

Ionic

Carbon atoms always have how many covalent bonds?

4

An atom of chlorine has how many valence electrons?

7

Copper and chlorine form an ionic compound whose formula is CuCl₂. The name of this compound is __________

copper (II) chloride

Iodine-131 decays by beta emission to

Xenon-131

In ionic compounds, __________ lose their valence electrons to form positively charged __________. 

metals; cations

True or false: The mass of the atom is almost all in the nucleus.

True

True or false: In beta decay the atomic number and mass number increase by 1.

False

True or false: Isotopes have the same atomic number but different mass numbers.

True

Predict the chemical formula of the compound that forms from aluminum and oxygen.

Al₂O₃

How many valence electrons does Group 15 have?

5

How many valence electrons does Group 16 have?

6

How many valence electrons does Group 17 have?

7

How many valence electrons does Group 18 have?

8, except helium, which has 2.

What is nuclear radiation?

Spontaneous energy from the nucleus

What are radioactive elements?

Elements that emit radiation

What are radioisotopes?

Radioactive isotopes.

What is radioactive decay?

The process by which unstable isotopes become stable by spontaneously emitting radiation and forming a daughter nuclide.

What is a daughter nuclide?

The new isotope formed during radioactive decay.

What is a nuclear decay equation?

Radioactive nucleus → daughter nuclide + radiation emitted

What is half-life?

50% remains.

What happens after two half-lives?

25% remains

What happens after three half-lives?

12.5% remains.

What formula can be used for radioactive decay?

Remaining amount = initial amount × (1/2)ⁿ

What is an alpha particle?

A positively charged particle with a 2+ charge; a helium nucleus

What is the symbol for alpha radiation?

⁴₂α

How far can alpha radiation travel in air?

A few centimeters

Can alpha radiation penetrate the skin?

It stops at the skin surface

What is beta radiation?

A negatively charged 1− high-energy electron.

What is the symbol for beta radiation?

⁰₋₁β

How far can beta radiation travel in air?

A few meters

Can beta radiation penetrate past the skin layer?

No

What is gamma radiation?

A neutral, high-energy light wave

What is the symbol for gamma radiation?

⁰₀γ

How far can gamma radiation travel in air?

Several hundred meters

Can gamma radiation penetrate the body?

Yes; it fully penetrates the body

Which has the greatest penetrating power: alpha, beta, x-ray, or gamma?

Gamma

Put radiation types in order of increasing penetrating power.

Alpha → beta → x-ray → gamma

What is electromagnetic radiation?

Energy that travels through space as a wave

What is another term for electromagnetic radiation?

Light/light wave

What is the speed of light?

3 × 10⁸ m/s.

What is wavelength?

The distance from the top of one wave crest to the top of the next

How is wavelength related to energy?

Wavelength is inversely proportional to energy

What is ionizing radiation?

Higher-energy radiation whose energy can be transferred to other atoms it collides with

What is penetrating power?

The ability to pass through matter

What is acute radiation exposure?

A single large dose

What is chronic radiation exposure?

Many smaller doses

What type of exposure causes radiation sickness?

Acute exposure

What does gray (Gy) measure?

The amount of radiation absorbed by an individual

What does sievert (Sv) measure?

Biological effective dose, considering penetrating power

What is a pure substance?

Matter made up of only one substance with fixed composition and distinct proportions