Chapter 15 Study Guide
How many electrons can occupy the first shell? How many can occupy the second shell?
2 electrons in the first shell, 8 in the second shell.
Is the transfer of an electron from a sodium atom to a chlorine atom a physical change or a chemical change?
A chemical change involves the formation of new material, thus, this or any other electron transfer, because it results in for formation of a new substance, is a chemical change.
What is an alloy?
A mixture composed of two or more metallic elements.
Which elements tend to form covalent bonds?
An atom that is attracted to an unpaired valence elecron of another atom resulting in a situation where the two are attracted mutually to the same electrons. Co- signifies sharing and -valent indicates that valence electrons are being shared.
What is the chemical formula for the ionic compound magnesium oxide?
Because magnesium is a group 2 element, you know a magnesium atom must lose two electrons to form a Mg2+ ion. Because oxygen is a group 16 element, an oxygen atom gains two electrons to form an O2- ion. These charges balance in a one-to-one ratio, and so the formula for magnesium oxide is MgO.
Acetate ion
CH3CO2-
Cyanide ion
CN-
Carbonate ion
CO32-
Why does the fluorine atom tend to gain only one electron?
Fluorine has one electron in the valence shell that is not paired, so it has an empty space to fill for that shell to be maxed out and balanced.
How many electrons are shared in a double covalent bond?
Four shared electrons.
Hydronium ion
H3O+
Bicarbonate ion
HCO3-
How is the number of unpaired valence electrons in an atom related to the number of bonds that the atom can form?
If a valence shell has 8 positions to max out that shell, but only has 4 electrons, that means there are 4 electrons available for their pairs to max out at 8. There are 4 available bonds.
List these bonds in order of increasing polarity: P--F, S--F, Ga--F, Ge--F(F, fluorine, atomic number 9; P ,phosphorus, atomic number 15; S, sulfur, atomic number 16; Ga, gallium, atomic number 31;Ge, germanium, atomic number 32).
Increasing polarity is S--F<P--F<Ge--F<Ga--F
Why does the magnesium atom tend to form the 2+ ion?
Magnesium is on the left of the periodic table, and so atoms of this element do not hold onto the two valence electrons very strongly. Because these electrons are not held very tightly, they are easily lost, which is why the magnesium atom tends to form the 2+ ion.
Ammonium ion
NH4+
Nitrate ion
NO3-
Why doesn't the neon atom tend to lose or gain any electrons?
Neon wont gain or lose anything because it has a net charge of 10. Meaning there are 10 protons and 10 electrons (2 first shell, 8 in the second, all maxed out)
Hydroxide ion
OH-
How many more electrons can fit in the valence shell of a hydrogen atom?
One more since there is already one electron in the shell, and it is the first shell which can hold a max of 2 electrons.
Phosphate ion
PO43-
Sulfate ion
SO42-
The valence electron of a sodium atom does not sense the full 11+ of the sodium nucleus. Why not?
The electrons in the valence shell are just one, because the inner shells have 2 and 8, maxing out those shells. The lone electron in the valence shell isn't going to fill the max power of that shell, which can hold 8 total, so it just leaves, leaving it as a positive ion.
What type of ion does the magnesium atom, Mg, tend to form?
The magnesium atom (atomic number 12) is found in group 2 and has two valence electrons to lose. Therefore, it tends to form the 2+ ion.
Do metals more readily gain or lose electrons?
The outer electrons of most metal atoms tend to be weakly held to the atomic nucleus. Consequently, these electrons are easily dislodged, leaving behind positively charged metal ions.
How do the electron-dot structures of elements in the same group in the periodic table compare with one another?
They have the same number of dots.
Which elements tend to form ionic bonds?
Two oppositely charged ions.
How many electrons make up a covalent bond?
Two, one from each participating atom.
Where are valence electrons located, and why are they important?
Valence electrons are located in the outermost occupied shell of an atom. They are important because they play a leading role in determining the chemical properties of the atom.
Which electrons are represented by an electron-dot structure?
Valence electrons which are the electrons that occupy the outermost shell of an atom.
To become a negative ion, does an atom lose or gain electrons?
When electrons are gained, electrons outnumber protons and the ion has a negative net charge.
How does an ion differ from an atom?
When the number of protons in the nucleus of an atom equals the number of electrons, the charges balance and the atom is electrically neutral. If one or more electrons are lost or gained, the balance is upset and the atom takes on a net electric charge. Any atom with a net electric charge is an ion.
