How is a single covalent bond formed?
Two atoms share two electrons.
You are asked to indicate the type and number of atoms in a molecule. Which representation would work best?
molecular formula
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
When the atoms involved in a covalent bond have the same electronegativity, what type of bond results?
a nonpolar covalent bond
An atom has four electrons in its valence shell. What types of covalent bonds is it capable of forming?
single, double, or triple
Elements found on the left side of the periodic table contain outer shells that are ________; these elements tend to form ________ in solution.
almost empty; cations
If an atom has a charge of +1, which of the following must be true?
It has one more proton than it does electrons.
Refer to the following figure to answer the questions below.
Based on electron configuration, which of the elements in the
figure would exhibit a chemical behavior most like that of oxygen?
sulfur
Refer to the following figure to answer the questions below.
How many electrons are involved in a triple covalent bond?
6
Refer to the following figure to answer the questions below.
What causes the shape of the molecule shown?
the shape of the sp3 hybrid orbitals of the electrons shared between the carbon and hydrogen atoms
Refer to the following figure to answer the questions below.
What is the atomic number of the cation formed in the reaction
in the illustration?
11
Refer to the following figure to answer the questions below.
What results from the chemical reaction in the illustration? The
reactants have no charge.
a cation with a net charge of +1 and an anion with a net charge of -1
What is the maximum number of hydrogen atoms that can be covalently bonded in a molecule containing two carbon atoms?
six
Van der Waals interactions may result when ________.
electrons are not symmetrically distributed in a molecule
Which of the following is broken when water evaporates?
hydrogen bonds
Which bond or interaction would be difficult to disrupt when compounds are put into water?
covalent bonds between carbon atoms
How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4?
two
The atomic number of chlorine is 17. The atomic number of magnesium is 12. What is the formula for magnesium chloride?
MgCl2
What is the difference between covalent bonds and ionic bonds?
Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between charged atoms.
A covalent bond is likely to be polar when ________.
one of the atoms sharing electrons is more electronegative than the other atom
In the following structure where A and B represent two different elements, the valency of A is ________ and B is ________.
one; three
Bonds between two atoms that are equally electronegative are ________.
nonpolar covalent bonds
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.
What is the maximum number of covalent bonds that an oxygen atom with atomic number 8 can make with hydrogen?
2
A covalent chemical bond is one in which ________.
outer-shell electrons of two atoms are shared so as to satisfactorily fill their respective orbitals
Which one of the atoms shown would be most likely to form an anion with a charge of -1?
one with 9 electrons
Which one of the atoms shown would be most likely to form a cation with a charge of +1?
one with 3 electrons
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
When are atoms most stable?
when all of the electron orbitals in the valence shell are filled
Which of the following is the best description of an atom's physical structure?
Atoms are little bubbles of space with mass concentrated at the center of the bubble.
Can the atomic mass of an element vary?
Yes. Adding or losing neutrons will change the atomic mass without forming a different element.
Elements 72Zn, 75As, and 74Ge have the ________.
same number of neutrons
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
Refer to the following figure to answer the questions below.
How many electrons will a single atom of sulfur with no charge
and no bonds have in its valence shell?
6
Refer to the following figure to answer the questions below.
12
Refer to the following figure (first three rows of the periodic
table) to answer the questions below.
Which pair of
elements would likely have similar valency and thus similar chemical behavior?
nitrogen and phosphorus
efer to the following figure (first three rows of the periodic table)
to answer the questions below.
What element does not
prefer to react with other elements?
helium
In a chemical reaction, the element 13Al will most preferably ________.
lose three electrons and become positively charged
A neutral atom has two, eight, eight electrons in its first, second, and third energy levels. This information ________.
does not tell us about the atomic mass of the element
The left to right order of elements in the periodic table is based on their ________.
atomic number
The atomic number of nitrogen is 7. Nitrogen-15 has a greater mass number than nitrogen-14 because the atomic nucleus of nitrogen-15 contains ________.
8 neutrons
A(n) ________ has charge but negligible mass, whereas a(n) ________ has mass but no charge.
electron; neutron
Carbon-14 has the same ________.
number of protons but more neutrons than carbon-12
Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers from 92-100. Which of the following can be true?
Molybdenum atoms can have between 50 and 58 neutrons.
An ion with six protons, seven neutrons, and a charge of 2+ has an atomic number of ________.
six
Atoms have no electric charge because they have ________.
an equal number of protons and electrons
Which of the following are compounds?
H2O and CH4, but not O2
Which of the following statements is TRUE?
Some naturally occurring elements are toxic to organisms.
Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by humans and other vertebrates, but not by other organisms such as bacteria or plants?
iodine
About 25 of the 92 natural elements are known to be essential to life. Which 4 of these 25 elements make up approximately 96% of living matter?
carbon, hydrogen, nitrogen, oxygen