The mass number of an atom is 15, and its atomic number is 7. The atom probably has… A) 8 neutrons in the nucleus. |
8 neutrons in the nucleus |
Which statement is true of atoms? A) Electrons determine the atom’s size. |
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 … A) the first shell must fill before the second shell can have electrons. |
the first shell shouldn’t have 3 electrons |
Which statement is true of the energy levels of electrons in shells? A) All the electrons in an atom have similar amounts of energy. |
The valence shell has higher energy than other occupied shells |
Two atoms always represent the same element if they have … A) the same number of electrons. |
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 _____________________. A) C; it has 6 protons. |
C; it has 6 protons |
An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have … A) 7 electrons. |
10 neutrons |
Radioactive decay is likely to occur when … A) an atom has too many electrons. |
an atom has too many neutrons |
Which statement is most useful in explaining why chemists assign atoms to chemical elements by counting protons? A) Protons at the atom’s surface determine the atom’s behavior. |
None of these. Elements are defined by the number of protons |
Covalent bonds hold atoms together because they … A) (a) fill shells without giving atoms much charge. |
do both (a) and (b) |
In molecules, C, H, O, and N atoms usually make __, __, __, and __ bonds respectively. A) 4, 1, 2, 3 |
4, 1, 2, 3 |
An atom’s atomic number is 7. Its valence is most likely … A) 5 |
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? A) The atom lost electrons from other shells. |
Shared electrons aren’t always near oxygen |
In a double covalent bond, a carbon atom shares … A) electrons in two orbitals. |
electrons in two orbitals |
Two C atoms form a double bond. Each C is bound to two H atoms. Which statement is true? A) The bonds orient in a tetrahedral fashion. |
All the atoms lie in a plane |
Partial charges occur when … A) (a) a covalent bond links atoms of two kinds. |
(b) atoms share electrons unequally |
To fill the valence shell, an electrically neutral, unbonded atom with atomic number 8 must add … A) 3 electrons. |
2 electrons |
Which answer helps to explain why carbon atoms tend to make 4 covalent bonds? A) The carbon nucleus has 4 protons. |
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? A) 4 |
1 |
A phrase that applies to covalent bonding and not other kinds of bonds is … A) paired electrons. |
electron-sharing |
When chemists and biologists want to show how atoms are bonded in a molecule, they usually use a … A) space-filling model. |
structural formula |
Polar attractions are … A) (a) forces between atoms with partial charges. |
(a), (b), and (c) are correct |
Hydrogen bonds … A) can form between H and N. |
can form between H and N |
Compared to covalent bonds, ionic bonds … A) have less bond energy. |
rely much less on electron-sharing |
A cation with two units of charge has 10 neutrons and 8 protons. The ion also has … A) 8 electrons. |
6 electrons |
True or false: Ions may form by transferring an atomic nucleus (with or without electrons) to another molecule. A) False |
True |
Which answer correctly ranks the atoms in terms of decreasing electronegativity (the highest electronegativity first)? A) N, O, C, H |
O, N, C, H |
Dr. Haxton says the O-O bond is polar and the C-C bond is nonpolar. A good student would say … A) Right! O is electronegative, so O2 is polar. |
Wrong again, Ralph. Both bonds are nonpolar |
Use your knowledge of electronegativity to pick out the most polar bond in the list below. A) C-H |
O-H |
If you want a molecule that is highly polar, look for one that contains: A) S-H |
H-N |
Which biological activity does NOT directly involve proteins? A) Sensing light. |
None of the above; proteins are involved in all of them |
Atoms and Molecules
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