Atomic number is equal to the number of neutrons in an atom's nucleus.
True
False
answer
False:
The atomic number of any atom is equal to the number of protons, not neutrons, in its nucleus
question
Which particle is indicated by the arrow?
electron
proton
neuron
atom
answer
proton:
Note how the number of the indicated particles in each of the three atoms defines each as a unique element.
question
The three atoms shown represent three unique ______.
cells
isotopes
molecules
elements
answer
elements:
The three atoms each contain different numbers of protons and are therefore unique elements
question
What do these four elements have in common?
They all have the same number of electrons in their first electron shell.
They are all generally unreactive elements.
They all have an incomplete valence electron shell.
They all have the same number of protons in their nuclei
answer
They all have an incomplete valence electron shell:
The valence shell is the outermost electron energy level. Valence shell electrons determine the reactivity of an element
question
If an oxygen atom were to form a chemical bond in which it gained two electrons, it would ______.
become less stable
not change in terms of relative stability
become more stable
answer
become more stable:
The addition of two electrons to the second electron shell of an oxygen atom would complete that energy level and result in increased stability.
question
How many hydrogen atoms will nitrogen bond with to form a stable molecule?
2
1
3
5
answer
3:
Nitrogen has 5 electrons in its valence (outermost) electron shell. Therefore, it will form covalent bonds with three hydrogen atoms. Each single covalent bond includes the sharing of three pairs of electrons. The three electrons contributed by the hydrogen atoms will fill the valence shell of nitrogen.
question
Sulfur is atomic number 16. Sulfur will form chemical bonds in a similar manner as ______.
hydrogen
oxygen
carbon
nitrogen.
answer
oxygen:
Oxygen and sulfur both have six electrons in their valence (outermost) electron shells. Therefore, they will form similar types and numbers of bonds with other atoms.
question
This figure depicts the formation of a(n) ______.
nonpolar covalent bond
hydrogen bond
polar covalent bond
ionic bond
answer
ionic bond:
An ionic bond is formed during the complete transfer of one or more electrons from one atom to another
question
Based on the information in this figure, we can conclude that chlorine has an atomic number of ______.
11
10
17
18
answer
17:
The unbonded chlorine atom has 17 electrons. Therefore, chlorine must have 17 protons and an atomic number of 17
question
After the transfer of the electron, sodium will form an ion with ______.
a charge of -1
a charge of +1
an atomic number of 18
an atomic number of 10
answer
a charge of +1 :
If sodium loses an electron, it will be positively charged. Although not shown explicitly in the figure, the element sodium contains 11 protons within its nucleus. If sodium forms a cation containing 10 electrons, it will have a charge of +1.
question
What holds the sodium and chloride ions together in a chemical bond?
the sharing of a pair of protons
the sharing of a pair of electrons
the attraction between their respective nuclei
an electrical attraction between opposite charges
answer
an electrical attraction between opposite charges:
The transfer of an electron results in ions with opposite charges that are electrically attracted to each other
question
How many valence shell electrons does the element carbon have?
2
8
4
6
answer
4:
Carbon is atomic number 6 and has four electrons in its outermost (valence) electron shell.
question
Which of the following accurately describes what is occurring in the illustrated reaction?
A hydrogen bond is formed between carbon and the four hydrogen atoms.
An ionic bond is formed between carbon and the four hydrogen atoms.
A quadruple covalent bond is formed between carbon and one hydrogen atom.
A single covalent bond is formed between carbon and each of the four hydrogen atoms.
answer
A single covalent bond is formed between carbon and each of the four hydrogen atoms:
Carbon shares a pair of electrons with each of the four hydrogen atoms. A pair of shared electrons is the basis of a single covalent bond
question
What is the most significant factor in the formation of a covalent bond?
the attraction of a hydrogen atom nucleus to the electrons of another atom
the complete transfer of one or more electrons from one atom to another
the sharing of electron pairs between two atoms
the transfer of one or more protons from one atom to another
answer
the sharing of electron pairs between two atoms:
Covalent bonds are formed by the sharing of electrons between two reactive atoms
question
Bonds between carbon and hydrogen atoms (as depicted on the right side of the figure) are generally ______.
hydrogen bonds
polar covalent bonds
nonpolar covalent bonds
ionic bonds
answer
nonpolar covalent bonds:
Neither carbon nor hydrogen is considered electronegative atoms. Therefore, neither atom has an overly strong pull on shared electrons, and those electrons are shared equally within a nonpolar covalent bond.
question
What explains the negative charge on the oxygen atom within the water molecule?
Oxygen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen.
Hydrogen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen.
Protons are transferred from oxygen to hydrogen during the formation of an ionic bond.
Electrons are transferred from hydrogen to oxygen during the formation of an ionic bond.
answer
Oxygen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen:
Oxygen atoms are highly electronegative and pull electrons away from the electropositive hydrogen atom
question
What type of bond is formed between the oxygen atom of one water molecule and the hydrogen atom of another water molecule?
polar covalent bond
ionic bond
hydrogen bond
nonpolar covalent bond
answer
hydrogen bond:
The attraction between the slightly negative oxygen atom of one molecule and the slightly positively charged hydrogen atom within a separate water molecule is the basis of hydrogen bond formation.
question
The lines drawn between hydrogen (H) atoms and the oxygen (O) atom in the structural diagram presented in the right of the figure each represent a ______.
hydrogen bond
polar covalent bond
nonpolar covalent bond
ionic bond
answer
polar covalent bond:
A covalent bond in which electrons are shared unequally is termed a polar covalent bond.
question
The chloride ion (Cl-) indicated by the arrow is interacting most closely with which of the following?
an oxygen atom within a water molecule
a hydrogen atom within a water molecule
another chloride ion
a sodium ion
answer
a hydrogen atom within a water molecule:
The negatively charged chloride anion has dissociated from the salt crystal and formed an interaction with the positively charged hydrogen atoms of several water molecules.
question
Which of the following is TRUE regarding the pH of a solution?
The more hydrogen ions in a solution, the more acidic the solution is.
The fewer hydrogen ions in a solution, the more acidic the solution is.
The more hydroxyl ions in a solution, the more acidic the solution is.
The fewer hydroxyl ions in a solution, the more basic the solution is.
answer
The more hydrogen ions in a solution, the more acidic the solution is:
The more hydrogen ions in a solution, the more acidic the solution is.
question
What is the classification of a solution with a pH of 8.3?
acidic solution
alkaline solution
neutral solution
buffered solution
answer
alkaline solution:
A pH between 0.0 and 7.0 is acidic. A pH between 7.0 and 14.0 is basic. Therefore, a solution with a pH of 8.3 is an alkaline (or basic) solution.
question
Salts are always ________.
double covalent compounds
ionic compounds
single covalent compounds
hydrogen bonded
answer
ionic compounds
question
Hydrogen bonds are comparatively strong bonds.
True
False
answer
False
question
A solution that has a pH of 2 could best be described as being ________.
acidic
slightly acidic
basic
neutral
answer
acidic
question
Buffers help to stabilize blood pH.
True
False
answer
True:
Buffers are essential for stabilizing the pH of body fluids (such as blood). Note: buffers cannot prevent a change in pH, they can only resist or minimize the change (if acids or bases are added to the buffered solution).
question
The lower the pH, the higher the hydrogen ion concentration.
True
False
answer
True
question
Which of the following is an example of a decomposition reaction?
H2 + O → H2O
MgSO4 + 2NaCl → MgCl2 + Na2SO4
2Na + Cl2 → 2NaCl
MgO2 → Mg + O2
answer
MgO2 → Mg + O2:
A decomposition reaction occurs when a larger molecule is broken down into smaller molecules or its constituent atoms.
question
A chemical reaction in which bonds are broken is usually associated with ________.
the consumption of energy
a synthesis
forming a larger molecule
the release of energy
answer
the release of energy
question
Amino acids joining together to make a peptide is a good example of a(n) ________ reaction.
decomposition
synthesis
exchange
reversible
answer
synthesis
question
Which of the following is not considered a factor in influencing a reaction?
time
particle size
temperature
concentration
answer
time
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