Chapter 2

What type of bond is joining the two hydrogen atoms?

Covalent

A(n) _____ refers to two or more atoms held together by covalent bonds.

molecule

What name is given to the bond between water molecules?

hydrogen

What type of bond joins the carbon atom to each of the hydrogen atoms?

single (nonpolar) covalent

The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound.

H2S

What happens when two atoms form a chemical bond?

A chemical bond forms when two atoms transfer or share outer electrons to complete their outer shells

Which of the following subatomic particles always has a positive charge?

proton

Electrons are held in an atom by attraction to what particle or location?

Attraction to the positively charged protons in the nucleus

What can happen to an electron when sunlight hits it?

it can stay in its original shell

it can move out to a higher electron shell

When an electron absorbs the required amount of light energy, it moves from a

Lower electron shell to a Higher electron shell, which is Farther from the nucleus.

When an electron loses a discrete amount of energy, it moves from a

higher electron shell to a lower electron shell, which is closer the nucleus.

A carbon atom and a hydrogen atom form what type of bond in a molecule?

Non polar covalent bond

Hydrogen bonding is most often seen

when hydrogen is covalently bonded to an electronegative atom

What does the term electron orbital describe?

An electron orbital describes a three-dimensional space where an electron can be found 90% of the time.

Which statement about relative potential energy of electrons is correct?

An electron in the 3p orbital of the third electron shell has more potential energy than an electron in the 2p orbital of the second electron shell.

A(n) _____ refers to two or more atoms held together by covalent bonds

Molecule

In the term trace element, the adjective trace means that?

The element is required in very small amounts.

Compared with 31P, the radioactive isotope 32P has

one more neutron

The reactivity of an atom arises from

the existence of unpaired electrons in the valence shell.

Which statement is true of all atoms that are anions?

The atom has more electrons than protons.

Which of the following statements correctly describes any chemical reaction that has reached equilibrium?

The rates of the forward and reverse reactions are equal.

We can represent atoms by listing the number of protons, neutrons, and electrons

−

−for example,

−2p+,2n0,2e− for helium. Which of the following represents the

18

O

18O isotope of oxygen?

8p + ,10 n 0 ,8 e−

What coefficients must be placed in the following blanks so that all atoms are accounted for in the products?

C6H12O6→_____C2H6O+_____CO2

2, 2

Which of the following bonds can form between atoms of equal electronegativity?

Van der Waals interactions can form between atoms of equal electronegativity.

Which statement about weak bonds is correct?

Weak bonds are transient and easily reversible.

Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by all forms of life?

iron

Which of the following are compounds?

H2O and CH4, but not O2

A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) __________.

element

Which of the following is a trace element found in the human body?

Magnesium

About 25 of the 92 natural elements are known to be essential to life. Four of these 25 elements make up approximately 96% of living matter. Which of the following elements account for most of the remaining 4% of an organism's mass?

calcium, potassium, phosphorus, sulfur

Which of the following statements is TRUE?

Some naturally occurring elements are toxic to organisms

What is the mass number of an ion with 108 electrons, 157 neutrons, and a +1 charge?

264

A. What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?

6

Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?

10

An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?

5

The innermost electron shell of an atom can hold up to _____ electrons.

2

Which of these relationships is true of an uncharged atom?

The number of protons is equal to the number of electrons

What determines the types of chemical reactions that an atom participates in?

the number of electrons in the outermost electron shell

The mass number of an atom is 15, and its atomic number is 7. The atom probably has...

8 neutrons in the nucleus

Which statement is true of atoms?

Electrons determine the atom's size

Dr. Jones says an atom has 3 electrons in the first shell and four electrons in the second shell. Someone should tell Dr. Jones that ..

the first shell shouldn't have 3

Which statement is true of the energy levels of electrons in shells?

The valence shell has higher energy than other occupied

Two atoms always represent the same element if they have ...

The same number of protons

An atom has 6 electrons, 6 protons, and 6 neutrons. You can tell that this atom belongs to the element _____ because _____________________.

C; it has 6 protons.

An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have

10 neutrons

Radioactive decay is likely to occur when

an atom has too many neutrons

Chemists assign atoms to chemical elements by counting their ________.

protons

Changing the number of __________ would change an atom into an atom of a different element.

protons in an atom

The atoms of different phosphorus isotopes _____.

Have different number of neutrons

The type of bonding and the number of covalent bonds an atom can form with other atoms is determined by __________.

the number of unpaired electrons in the valence shell

Atoms have no electric charge because they have ________.

An equal number of protons and electrons

An ion with six protons, seven neutrons, and a charge of 2+ has an atomic number of ________.

six

Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers from 92-100. Based on this information, which of the following is also true of molybdenum?

Molybdenum atoms can have between 50 and 58 neutrons.

A neutral atom has 2, 8, 8 electrons in its first, second, and third energy levels. This information ________.

does not tell us about the atomic mass of the element

Which pair of elements is most likely to react if bought together?

sodium and chlorine

How many electrons are present in a Phosphorus 2+ atom?

13

how many electrons will a single atom of nitrogen with no charge and no bonds have in its valence shell?

5

Oxygen has an atomic number of 8 and, most commonly, a mass number of 16. Thus, what is the atomic mass of an oxygen atom?

Approximately 16 daltons

Elements 72Zn, 75As, and 74Ge have the same number of ________.

Neutrons

Under which of the following conditions will an atom be the most stable?

When all of the electron orbitals in the valence shell are filled

Atoms with the same number of protons but with different electrical charges _____.

Are different ions

In salt, what is the nature of the bond between sodium and chlorine?

ionic

An ionic bond involves

an attraction between ions of opposite charge

A phrase that applies to covalent bonding and not other kinds of bonds is

Electron-sharing

Covalent bonds hold atoms together because they ...

Do both (a) and (b)

An atom's atomic number is 7. Its valence is most likely

3

By making two covalent bonds, an O atom (with 8 protons) fills its valence shell. Why does the atom's charge stay close to zero?

Shared electrons aren't always near oxygen

In a double covalent bond, a carbon atom shares ..

electrons in two orbitals

To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add

2 electrons

Which answer helps to explain why carbon atoms tend to make 4 covalent bonds?

The valence shell needs 8 electrons

An electrically neutral molecule has the formula C3H4O2N. If the carbon atoms form the usual number of bonds, how many covalent bonds will each hydrogen atom have with other atoms in the molecule?

1

f you want a molecule that is highly polar, look for one that contains:

H-N

an ionic bond is formed when __________.

one atom transfers an electron to another atom

A salamander relies on hydrogen bonding to stick to various surfaces. Therefore, a salamander would have the greatest difficulty clinging to a ________.

surface of hydrocarbons

Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?

Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.

The atomic number of chlorine is 17. The atomic number of magnesium is 12. Given this information, what is the formula for magnesium chloride?

MgC12

Van der Waals interactions may result under which of the following conditions?

electrons are not symmetrically distributed in a molecule

If an atom has a charge of +1, which of the following must be true?

It has one more proton than it does electrons.

Elements found in the first two columns of the periodic table contain outer electron shells that are ________; these elements tend to form ________ in solution.

almost empty; cations

An atom has four electrons in its valence shell. What types of covalent bonds is it capable of forming?

single, double, or triple

A covalent bond is likely to be polar under which of the following conditions?

one of the atoms sharing electrons is more electronegative than the other atom

How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4?

Two

Which of the following types of bond is broken when water evaporates?

Hydrogen bonds

How many electrons participate in a triple covalent bond?

6

Based on electron configuration, which of the elements would exhibit a chemical behavior similar to oxygen?

Sulfer

Nitrogen (N) normally forms three covalent bonds with a valence of five. However, ammonium has four covalent bonds, each to a different hydrogen (H) atom (H has a valence of one). What do you predict to be the charge on ammonium?

+1

Which of the following types of representation would work best to indicate the type and number of atoms in a molecule?

molecular formula

How is a covalent bond formed

two atoms share two electrons

Chemical equilibrium is reached when _____.

the forward and reverse reactions occur at the same rate so that the concentrations of reactants and products remain the same

Which of the following correctly describes chemical equilibrium?

Forward and reverse reactions continue with no net effect on the concentrations of the reactants and products

Which of the following lists some of the levels of biological organization from less complex to more complex?

atoms, molecules, cells, organs

Which of the following is a true statement about how living organisms use energy and chemicals to carry out life's activities?

Energy flows through an ecosystem, but chemicals cycle within it.

Which the following statements about Darwin's theory of natural selection is true?

Individuals with inherited traits that are better suited to the local environment are more likely to survive and reproduce than less well-suited individuals.