Mastering Biology Ch 2 H.W.
The innermost electron shell of an atom can hold up to ________ electrons.
2
An atom's atomic number is 7. Its valence is most likely ...
3
The mass number of an atom is 15, and its atomic number is 7. The atom probaly has...
8 neutrons in the nucleus
Electrons are held in an atom bt attraction to what particle or location?
Attraction to the postively charged protons in the nucleus
Sort the subatomic particles according to their masses.
Mass of ~ 1 amu- proton, neutron Mass of ~ 1/2000 amu- electron
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.
O-H
Chemists assign atoms to chemical elements by counting their _____.
Protons
Atoms with the same number of protons but with different electrical charges _____.
are different ions
Without making or breaking bonds, the pictured molecule can change its shape because ...
rotation can occur around single bonds
An atom has 8 protons, 8 neutrons, and 8 electrons. Another isotope of the same element might have ...
10 neutrons
Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?
10
An electrically neutral molecule has the formula C3H4O2N. If the carbon aroms in the molecule?
1
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
Which statement is true of atoms?
Electrons determine the atom's size.
Which atom in the pictured molecule will have the strongest partial positive change?
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 statement is true of the energy levels of electrons in shells?
The valance shell has higher energy than other occupied shells
Radioactive decay is likely to occur when...
an atom has too many neutrons.
A(n) ____ bond joins these two oxygen atoms.
double covalent
In a double covalent bond, a carbon atoms shares...
electrons in two orbitals
What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
6
The ammonia molecule in the diagram has the observed bond orientation because ...
All of the above - N has four pairs of electrons in the valance shell - N has 7 protons in it nucleus - Electrons repel one another
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
Partial charges occur when...
Both a & b (A: a covalent bond links atoms of two kinds, b: atoms share electrons unequally)
Covalent bonds hold atoms together because they...
Both a & b (A: fills shells without giving atoms much change, B: bring electrons closer to 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
To fill the valance shell, an electrially neutral, unbonded atom with atomic number 8 must add...
2 electrons
This atom can form up to _____ single covalent bond(s).
4
If you want a molecule that is highly polar, look for one that contains:
H-N
The brackets are indicating a(n) _____ bond.
Hydrogen
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
What can happen to an electron when sunlight hits it?
It can move out to a higher electron shell, it can stay in its orginal shell
Match each property to the appropriate subatomic particle.
Proton: ( +1 charge, symbol p) Neutron: (0 charge, symbol n) Electron: (-1 charge, symbol e)
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 celectrons aren't always near oxygen
What determines the types of chemical reactions that an atom participates in?
The number of electrons in the outermost electron shell
Which of these relationships is true of an uncharged atom?
The number of protons is equal to the number of electrons
Which answer helps to explain why carbon atoms tend to make 4 covalent bonds?
The valance shell needs 8 electrons
Which of the following refers to atoms with the same atomic number but differerent 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
An ionic bond involves _____.
an attraction between ions of opposite charge
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
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
A(n) ____ refers to two or more atoms held together by covalent bonds.
molecule
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
Two atoms always represent the same element if they have ...
the same number of protons
