Chapter 2
If an element is composed of atoms with an atomic number of 6 and a mass number of 14, then a neutral atom of this element contains
6 protons and 8 neutrons
In an aqueous solution, sodium ions move toward
a negative terminal
By weight, which element is the second most abundant in the human body?
carbon
The molecule CO2 is known as
carbon dioxide
indicate which of these lists contains only trace elements
silicon, fluorine, tin
if a pair of electrons is unequally shared between two atoms, a ___ occurs
single covalent bond
In a molecule of nitrogen, three pairs of electrons are shared by two nitrogen atoms. The type of bond that is formed is an example of a
triple covalent bond
In hydrolysis reactions, compounds react with
water, causing decomposition
Helium (He) has an atomic number of 2. It is chemically stable because it
has a full outer electron shell
One mole of any element
has the same number of elements
The molecule H2 is known as
hydrogen
Which element commonly has only a proton as its nucleus
hydrogen
Elements that have atoms with full outer shells of electrons are
inert gases
the weakest bond b/t two single atoms would be the ___ bond
ionic
isotopes of an element differ int he number of
neutrons in the nucleus
The molecule NO is known as
nitric oxide
radioisotopes have unstable
nuclei
The molecule O2 is known as
oxygen
by weight, which element is the most plentiful in the human body
oxygen
the "atomic number" of an atom is determined by the number of ___ it has
protons
The mass of an atom is largely determined by the number of ___ it has
protons and neutrons
the "atomic weight" of an atom reflects the average number of
protons and neutrons
the mass number represents the number of
protons and neutrons
the nucleus of an atom consists of
protons and neutrons
the atomic number represents the number of
protons in an atom
the innermost electron shell in an atom holds up to ___ electrons
2
An unequal sharing of electrons result in what type of chemical bonds?
Polar covalent
The formula for methane gas is CH4. What does the formula 4CH4 represent?
4 molecules, each containing a carbon atom and 4 hydrogen atoms
If an isotope of oxygen has 8 protons, 10 neutrons and 8 electrons its mass number is
18
Oxygen (atomic number 8) requires how many additional electrons to fill its outer electron shell?
2
Magnesium atoms have two electrons in the outermost shell. As a result, you would expect magnesium to form ions with a charge of
+2
Sodium (Na) has an atomic number of 11. How many electrons are in the outer electron shell of a neutral sodium atom?
1
Magnesium atoms have two electrons in the outermost shell and chlorine atoms have seven. The compound magnesium chloride would contain
1 magnesium and 2 chlorine
Which of the following is not a cation?
Cl-
What about hydrogen bonds is false?
Hydrogen bonds are strong attractive forces b/t hydrogen atoms and negatively charged atoms
In chemical notation, the symbol Ca2+ means ___
a calcium ion that has lost two electrons
Ionic bonds are formed when
an electron or electrons are completely transferred from one atom to another
When electrons are transferred from one atom to another, the two atoms unite as a result of the opposite charges,
an ionic bond is formed
In an aqueous solution, cations are attracted toward
anions
The smallest stable units of matter are
atoms
In an ionic bond, the electron donor is the ___, whereas the electron acceptor is the ___
cation, anion
Ions with a + charge are called
cations
H20 is an example of a
compound
When atoms complete their outer electron shell by sharing electrons, they form
covalent bonds
The reaction A + B + energy → AB is an example of a(n)
endergonic reaction
A dust particle floating on a water surface illustrates
surface tension
AB → A + B is to decomposition as A + B → AB is to
synthesis
The reaction N2 + 3 H2 → 2 NH3 is an example of a(n)
synthesis reaction
Ions in an ionic molecule are held together due to
the attraction of opposite electrical charges
the chemical behavior of an atom is determined by
the outermost shell
