Ch 2

mass of ~1/2000 amu

electron

Refer to the following figure to answer the questions below. How many electrons are present in a Phosphorus 2+ atom? (^31 P , 15 below the P)

13 (15p-2 = 13e)

Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true?

All the atoms lie in a plane. (the double bond limits all the atoms to a plane)

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

10 neutrons. (same # of protons, diff # of neutrons)

What is the atomic number of the cation formed in the reaction in the illustration?

11

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 answer correctly ranks the atoms in terms of decreasing electronegativity (the highest electronegativity first)?

O,N,C,H (O:3.5, N:3.0, C:2.5, H:2.1)

Use your knowledge of electronegativity to pick out the most polar bond in the list below.

O-H (opposite ends of electronegativity scale so large polarity)

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

proton (each has one unit of positive charge)

Which of these figures correctly illustrates the nature of the bonding of H2O?

(see imagine) H has + charge, O has - charge. 4 electrons bc of outer valance shell

to fear: to love: of neither gender/type: loosening/split apart: first: to: water: fat: from, out of, remove:

-phob -phil neutr- -lysis proto- ad- hydro- lip- de-

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

8 neutrons in the nucleus.

We can represent atoms by listing the number of protons, neutrons, and electrons−−for example, 2p+,2n0,2e−2p+,2n0,2e− for helium. Which of the following represents the ^18O isotope of oxygen?

8p+, 10n^0, 8e^-

Which statement about relative potential energy of electrons is correct?

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

Which of the following are compounds?

H2O and CH4, but not O2

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

Hydrogen bond

Refer to the following figure to answer the questions below. 3H2 + N2 ↔ 2NH3 Which of the following factors will increase the rate of reaction in the forward direction?

addition of both nitrogen and hydrogen

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

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

molecular formula

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

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

the same number of protons.

Which of the following factors contribute to the tetrahedral shape of the above molecule?

the shape of the sp^3 hybrid orbitals of the electrons shared between the carbon and hydrogen atoms

three: against: many: two: single: with: four: first: not: equal:

tri- anti- poly- di- mono- co- quad- prim- non- iso-

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

two

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

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.

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.

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 (atomic mass = p + n)

How is a covalent bond formed?

two atoms share two 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

Which statement is true of the atom shown in the diagram?

1. An electron will move from the outer to the inner shell. 2. The atom is in the excited state. 3. The atom has more than one valence electron. (The atom has a vacancy in its inner shell; an electron has moved to the outer (valence) shell. The result is an unstable excited state. An electron will move back to the inner shell, restoring the ground state as the atom gives off energy.)

The ammonia molecule in the diagram has the observed bond orientation because ...

1. electrons repel one another. 2.N has four pairs of electrons in the valence shell. 3.N has 7 protons in its nucleus. (Since N has 7 protons, it must fill the second shell, giving it 4 pairs of electrons. The electrons form 3 bonds and 1 lone pair of electrons. Each pair of electrons repels the other pairs, so they are equally far apart.)

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

10

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

2

How many electrons will a single atom of nitrogen with no charge and no bonds have in its valence shell? (^14 N, 7 below the N)

2 (7 total e-'s, so 2 e's in first shell, 5 in 2nd shell)

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

2 electrons (The neutral atom has 8 electrons. Two electrons fill the first shell, and 6 go into the second (valence) shell. Two more electrons would fill the valence shell.)

What coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6→_____C2H6O+_____CO2

2; 2

This atom can form up to _____ single covalent bond(s).

4 (because there are four electrons in the outermost electron shell)

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

5 (atomic # = protons)

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

6

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

6

This/these atom/ions can form up to _____ single co-ordinate bond(s).

6 (max of 6 degenerate orbitals)

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

are different ions (ions are charged atoms)

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

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 electrons, it can only have 0, 1, or 2 electrons

Covalent bonds hold atoms together because they ...

(a) fill shells without giving atoms much charge. (b) bring electrons closer to protons.

subatomic particles: proton - neutron - electron -

+1 charge, p 0 charge, n -1 charge, e

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

3 (Two electrons fill the first shell, and 5 go into the second (valence) shell. The atom needs 3 more electrons to fill the valence shell.)

In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively.

4, 1, 2, 3

How many electrons participate in a triple covalent bond?

6

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. (We cannot know the exact location of an electron. Instead, we can describe a three-dimensional space in which an electron spends most of its time.)

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

Attraction to the positively charged protons in the nucleus (Electrons have a negative charge, and so are attracted to the positive charge of the protons in the nucleus, which holds them in the atom.)

Which statement is true of atoms?

Electrons determine the atom's size.

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.

What can happen to an electron when sunlight hits it?

It can (1) stay in its original shell, and (2) move out to a higher electron shell. (The electron will move out to a higher shell if the sunlight provides the correct, discrete amount of energy. If the sunlight does not provide the correct amount of energy, the electron will remain in its original shell.)

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

It has one more proton than it does electrons.

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

N-H

Which model most accurately represents the current view of the structure of the atom?

Probability Model (We cannot determine the exact motion of electrons. We can only compute the regions where electrons occur most of the time. To emphasize the uncertainty, a diagram showing random motion is more suitable than planetary paths.)

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. (Oxygen keeps 6 electrons to itself. The 4 shared electrons migrate between O and the other atoms, thus contributing 4 half-charges to oxygen. This gives oxygen about 8 units of negative charge, balancing the atom's 8 protons.)

Which of the following statements is TRUE?

Some naturally occurring elements are toxic to organisms.

Which atom in the pictured molecule will have the strongest partial positive charge?

The C that's in C=O. (This C atom is bound to the two most electronegative atoms in the molecule (O), both of which are pulling electrons from C.)

Which of these relationships is true of an uncharged atom?

The number of protons is equal to the number of electrons. (since its uncharged, In this situation the number of positive charges is equal to the number of negative charges)

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

The rates of the forward and reverse reactions are equal.

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

The valence shell has higher energy than other occupied shells. (The outer occupied shell is the valence shell, and outer shells hold electrons at higher energy than inner shells)

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

The valence shell needs 8 electrons.

Which of these refers to atoms with the same atomic number but different atomic masses?

These atoms are isotopes.

Dr. Haxton says the O-O bond is polar and the C-C bond is nonpolar. A good student would say ...

Wrong again, Ralph. Both bonds are nonpolar. (When two atoms of the same kind form a covalent bond, they share electrons equally because their electronegativity is the same.)

Considering that the reactants have no charge, what are the products of the reaction shown above?

a cation with a net charge of +1 and an anion with a net charge of -1

Partial charges occur when ...

a covalent bond links atoms of two kinds and atoms share electrons unequally.

Refer to the following figure to answer the questions below. 3H2 + N2 ↔↔ 2NH3 Which of the following is true for the above reaction?

ammonia is being formed and decomposed simultaneously

Radioactive decay is likely to occur when ...

an atom has too many neutrons. (The atomic nucleus becomes unstable if the ratio of protons to neutrons is too far from unity.)

What type of bond is joining the third hydrogen atom on the right to the oxygen atom?

co-ordinate bond (A co-ordinate covalent bond is one in which the both bonding electrons come from the same atom. It is also called a dative covalent bond.) picture: HOH + H ->

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

A(n) _____ bond joins these two oxygen atoms.

double covalent (the oxygen atoms are sharing two pairs of electrons)

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

electron-sharing (only covalent bonds have atoms that share electrons)

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

electrons are not symmetrically distributed in a molecule

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

electrons in two orbitals. (A double bond involves two orbitals, each with a shared pair of electrons.

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

element

The atoms of different phosphorus isotopes _____

have different numbers of neutrons (The phosphorus atom is defined by its proton number. Changes in neutron number alter the mass of the atom, but not its chemical behavior or reactivity.)

The brackets are indicating a(n) _____ bond.

hydrogen bond (a hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge.)

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

ionic (Sodium and chlorine ions are attracted to each other.)

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

An ionic bond is formed when __________.

one atom transfers an electron to another atom (Transfer of an electron from one atom to another results in a positive ion (cation) and a negative ion (anion), which usually attract each other to form an ionic bond. However, the ions need not have acquired their electrical charge due to an electron transfer with each other.)

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 (unequal)

In the following structure where A and B represent two different elements, the valency of A is ________ and B is ________.

one; three

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

protons in an atom

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

single (nonpolar) covalent (each carbon-hydrogen bond involves a single pair of equally shared electrons)

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

single, double, or triple

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

sulfur (same column)

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

In the term trace element, the adjective trace means that

the element is required in very small amounts.

The reactivity of an atom arises from

the existence of unpaired electrons in the valence shell

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

the number of electrons in the outermost electron shell (An atom is least likely to participate in a reaction when its outermost shell is stable.)

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 (The fullness of the valence shell determines the pattern of covalent bonding or ionization. The reactivity of an atom is a function of the presence of unpaired electrons in one or more orbitals of their valence shell.)

An ionic bond involves _____.

an attraction between ions of opposite charge

Atoms have no electric charge because they have ________.

an equal number of protons and electrons

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. (Only the electrons of atoms participate in chemical bonds, which form when atoms transfer or share outer or valence electrons.)

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.

What type of bond is joining the two hydrogen atoms?

Covalent Bond (electron pairs are shared.)

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 name is given to the bond between water molecules?

Hydrogen (A hydrogen atom with a net positive charge is attracted to an oxygen atom with a net 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?

MgCl2

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

Molecule (A molecule is defined as two or more atoms held together by covalent bonds.)

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.

Which statement is true of all atoms that are anions?

The atom has more electrons than protons.

Compare the three atom diagrams. Which one shows the electron with the highest potential energy?

The farther an electron shell is from the nucleus, the more potential energy an electron has to gain in order to move into it.

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

Van der Waals interactions can form between atoms of equal electronegativity. (Even nonpolar covalent bonds have temporary regions of partial positive and negative charge, due to the chance movements of electrons. Attractions between such transient positive and negative charges create weak Van der Waals interactions.)

Which statement about weak bonds is correct?

Weak bonds are transient and easily reversible.(Molecules that form weak bonds can come together, interact, and then separate. The combined effect of many weak and transient hydrogen bonds or Van der Waals interactions can produce important emergent properties.)

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

magnesium (accounts for only 0.1% of most living things - by weight)

mass of ~1 amu

neutron and proton

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

neutrons

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

non polar covalent bond (Atoms with similar electronegativities form nonpolar covalent bonds.) atomic mass # on periodic table* (H2, C6 are close)

Compared with ^31P , the radioactive isotope ^32P, has

one more neutron.

Chemists assign atoms to chemical elements by counting their ________.

protons

Without making or breaking bonds, the pictured molecule can change its shape because ...

rotation can occur around single bonds. (Rotation allows groups of atoms to change position while preserving the usual bond angles around each atom.)

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

sodium and chlorine

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

Hydrogen bonding is most often seen __________.

when hydrogen is covalently bonded to an electronegative atom (Highly electronegative atoms attract shared electrons more strongly than hydrogen does, resulting in a slight positive charge on the hydrogen atom. The slightly positive hydrogen atom is then attracted to another electronegative atom, forming a hydrogen bond.)