Chapter 2- Mastering Biology
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
What is the maximum number of covalent bonds that an oxygen atom with atomic number 8 can make with hydrogen?
2
An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?
5
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
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
What determines the types of chemical reactions that an atom participates in?
the number of electrons in the outermost electron shell
Which of these refers to atoms with the same atomic number but different atomic masses?
these atoms are isotopes
Hydrogen bonding is most often seen _____.
when hydrogen is covalently bonded to an electronegative atom
A covalent chemical bond is one in which _____.
outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms
Which of the following are compounds?
H2O and CH4, but not O2
Given what you know about the human body, what do you think accounts for the high percentage of oxygen (65.0%)?
The human body is made up mainly of water, and there is one oxygen atom in every water molecule.
An ionic bond is formed when _____.
one atom transfers an electron to another atom
How is a single covalent bond formed?
Two atoms share two electrons.
What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
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.
Electrons are held in an atom by attraction to what particle or location?
Attraction to the positively charged protons in the nucleus
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.
What can happen to an electron when sunlight hits it?
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.
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 these relationships is true of an uncharged atom?
The number of protons is equal to the number of electrons.
Which bond or interaction would be difficult to disrupt when compounds are put into water?
covalent bonds between carbon atoms
A(n) _____ bond joins these two oxygen atoms.
double covalent
A(n) ________ has charge but negligible mass, whereas a(n) ________ has mass but no charge.
electron; neutron
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 brackets are indicating a(n) _____ bond.
hydrogen bond
What name is given to the bond between water molecules?
hydrogen bond
Which of the following is broken when water evaporates?
hydrogen bonds
Which of the following is a trace element required by most living organisms?
manganese
A(n) _____ refers to two or more atoms held together by covalent bonds.
molecule
Which pair of elements would likely have similar valency and thus similar chemical behavior?
nitrogen and phosphorus
Which of the following subatomic particles always has a positive charge?
proton
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
What is the maximum number of hydrogen atoms that can be covalently bonded in a molecule containing two carbon atoms?
six
