Chapter 2 HW
Compare the three atom diagrams. Which one shows the electron with the highest potential energy?
**picture**
What type of bond joins the carbon atom to each of the hydrogen atoms?
**picture**
Which of the following models represents an atom that is most likely to form a cation with a charge of +1?
**picture**
Which of the following models represents an atom that is most likely to form an anion with a charge of -1?
**picture**
Which of these figures correctly illustrates the nature of the bonding of H2O?
**picture**
Proton
+1 charge, symbol p, ~1 amu
Electron
-1 charge, symbol e, ~1/2000 amu
Neutron
0 charge, symbol n, ~1 amu
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
Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?
10 (19-9)
An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have ...
10 neutrons
How many electrons are present in a Phosphorus 2+ atom?
13
The innermost electron shell of an atom can hold up to _____ electrons
2
To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add ...
2 electrons
What is the mass number of an ion with 104 electrons, 159 neutrons, and a +1 charge?
264 (104+159+1)
What coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6→_____C2H6O+_____CO2
2; 2
An atom's atomic number is 7. Its valence is most likely ...
3. The neutral atom has 7 electrons. 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.
This atom can form up to _____ single covalent bond(s).
4
In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively.
4, 1, 2, 3
An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?
5
How many electrons will a single atom of nitrogen with no charge and no bonds have in its valence shell?
5
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
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+,10n0,8e−
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.
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
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.
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
Electrons are held in an atom by attraction to what particle or location?
Attraction to the positively charged protons in the nucleus
Part complete 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.
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 statement is true of atoms?
Electrons determine the atom's size With electrons on the surface, atoms repel one another when they come too close. Thus, electrons determine the space that an atom occupies.
If you want a molecule that is highly polar, look for one that contains:
H-N
Which of the following are compounds?
H2O and CH4, but not O2
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
The brackets are indicating a(n) _____ bond.
Hydrogen
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.
If an atom has a charge of +1, which of the following must be true?
It has one more proton than it does electrons.
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
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.
The ammonia molecule in the diagram has the observed bond orientation because ...
N has 7 protons in its nucleus. N has four pairs of electrons in the valence shell. electrons repel one another.
Elements 72Zn, 75As, and 74Ge have the same number of ________.
Neutrons
Which answer correctly ranks the atoms in terms of decreasing electronegativity (the highest electronegativity first)?
O, N, C, H
Use your knowledge of electronegativity to pick out the most polar bond in the list below. N-H O-H O-N O-C C-H
O-H
Which model most accurately represents the current view of the structure of the atom?
Probability model
Which of the following subatomic particles always has a positive charge?
Proton
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
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.
Which statement is true of all atoms that are anions?
The atom has more electrons than protons.
Which statement is true of the atom shown in the diagram?
The atom is in the excited state. The atom has more than one valence electron. An electron will move from the outer to the inner shell.
Which of these relationships is true of an uncharged atom?
The number of protons is equal to the number of electrons
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.
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.
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. 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. Read about the importance of the transience of weak bonds such as hydrogen bonds, ionic bonds, and Van der Waals interactions.
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.
Partial charges occur when ...
a covalent bond links atoms of two kinds. atoms share electrons unequally.
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.
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
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
Atoms with the same number of protons but with different electrical charges _____.
are different ions
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
What type of bond is joining the two hydrogen atoms?
covalent
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
A phrase that applies to covalent bonding and not other kinds of bonds is ..
electron-sharing.
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
Covalent bonds hold atoms together because they ...
fill shells without giving atoms much charge. bring electrons closer to protons.
The atoms of different phosphorus isotopes _____.
have different numbers of neutrons
When an electron loses a discrete amount of energy, it moves from a _____ electron shell to a _____ electron shell, which is _____ the nucleus.
higher, lower, closer to
What name is given to the bond between water molecules?
hydrogen
In salt, what is the nature of the bond between sodium and chlorine?
ionic
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
When an electron absorbs the required amount of light energy, it moves from a _____ electron shell to a _____ electron shell, which is _____ the nucleus.
lower, higher, farther from
Which of the following is a trace element found in the human body?
magnesium
A(n) _____ refers to two or more atoms held together by covalent bonds.
molecule
A carbon atom and a hydrogen atom form what type of bond in a molecule?
nonpolar covalent bond
An ionic bond is formed when __________.
one atom transfers an electron to another atom
Compared with 31P, the radioactive isotope 32P has
one more neutron.
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
Without making or breaking bonds, the pictured molecule can change its shape because ...
rotation can occur around single bonds.
Which pair of elements is most likely to react if bought together?
sodium and chlorine
Part complete 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.
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.
What determines the types of chemical reactions that an atom participates in?
the number of electrons in the outermost electron shell
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
Two atoms always represent the same element if they have ...
the same number of protons.
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
