JLH Chem chapter 3 Flashcards
Individual atoms are rarely encountered in nature. Instead, atoms are far more commonly joined together to form compounds. What are the two types of chemical compounds?
Ionic compounds
Covalent compounds
Ionic compound
compounds composed of positively & negatively charged ions held together by strong electrostatic forces.
usually formed when a metal reacts with a nonmetal or polyatomic ion
NaCl (table salt)
What are electrostatic forces?
electrical attraction between oppositely charged ions.
Covalent compounds
compounds that composed of individual molecules, discrete groups of atoms that share electrons (share equally)
What are some examples of covalent compounds?
H2O
CH4 (Methane)
Methane is the main component of natural gas
what does Bonding mean?
joining of two atoms in a stable arrangement
What happens in bonding?
elements gain, lose, or share electrons to attain the electronic configuration of the noble gas closest to them in the periodic table.
Bonding involves only what of an atom?
the valence electrons
Ionic bond
result from the transfer of electrons from one element to another
Covalent bonds
result from the sharing of electrons between two atoms
Ionic bonds form between what elements on the periodic table?
ionic bonds form between a metal and a nonmetal
(NaCl)
What do covalent bonds form with?
two nonmetals or
metalloid and a nonmetal
molecule
compound or element containing two or more atoms joined by a covalent bond
When a metal and nonmetal combine, what is the bond?
(Na + I)
ionic bond
NaI
when two nonmetals combine, or a metalloid bonds with a nonmetal, what is the bond?
(H2 + O2)
covalent bond
(H2O2 hydrogen peroxide)
Is CO ionic or covalent
covalent
(both elements are nonmetals)
Is CaF2 ionic or covalent?
Ionic
Is this molecule an ionic bond or covalent bond?
Is it a compound or element?
- covalent bond
- compound
Is this molecule a compound or element?
(N2)
Element
remember, compounds are 2 different elements
Ionic compounds consist of oppositely charged ____ that have a strong _____________ __________
Ionic compounds consist of oppositely charged ions that have a strong electrostatic attraction
What are the two types of ions?
cations +
anions -
What type of ion has fewer electrons than protons?
cation
What type of ion has more electrons than protons?
anion
The nature and magnitude of the charge on an ion depend on what?
The position of an element in the periodic table.
In forming an ion, an atom of a main group element loses or gains electrons to obtain the electronic configuration of the noble gas closest to it in the periodic table
Sodium (group 1A) has an atomic number of 11, giving it 11 p & 11 e- in the neutral atom. This gives sodium one more electron than neon, the noble gas closest to it in the periodic table. What happens with Na to become more stable?
in losing one electron, sodium forms a cation with a +1 charge, which still has 11 protons, but now has only 10 electrons in its electron cloud (2 in first shell and 8 in 2nd shell).
1s22s22p63s1 → 1s22s22p6 (Na+)
Magnesium has two more electrons than neon, the noble gas closest to it in the periodic table. What happens with Mg in order to become more stable?
Mg has 2 valence electrons. Loss of these two valence electrons forms a magnesium cation, symbolized as Mg2+
1s22s22p63s2 → 1s22s22p6
What type of ions do metals form?
cations
Do cations change size from the atom they were when neutral?
Cations are smaller in size than the atoms from which they are formed because a cation has more protons than electrons, the positively charged nucleus pulls the remaining electrons closer.
What happens with chlorine in order to become more stable?
Neutral Cl has 17 electrons (one less electron than argon, the noble gas closest to it).
By gaining one electron, Cl forms an anion with a -1 charge (Cl-)
1s22s22p63s23p5 → 1s22s22p63s23p6
What type of ions are formed from nonmetals?
anions
by gaining one, two, or sometimes three electrons, an atom forms an anion with a completely filled outer shell of electrons.
Are anions larger or smaller than the atoms from which they are formed?
Larger, because an anion has more electrons than protons, the electrons are held less tightly by the positively charged nucleus, and the anion size is larger than the atom size.
how are ions written?
ions are written with the element symbol followed by a superscript to indicate the charge.
Na+, Mg2+, O2-
When is a main group element especially stable?
When it possesses an octet of electrons in its outer shell.
Identify the ion shown in the molecular art and give its ion symbol
Li+
1 more proton than electrons
Give the symbol for the ion shown
N3-
Because the number of protons equals the atomic number (quantity of p identifies the element). If the number of electrons is greater than the number of protons, the charge is negative (anion). If the number of protons is greater than the number of electrons, the charge is positive (cation). Write an ion symbol for an atom with 9 protons and 10 electrons.
F-
How many protons and electrons are present in Ca2+
O2-?
Ca2+ (20 p, 18 e-)
O2- (8p, 10 e-)
Which sphere (A or B) represents S and which represents S2-?
A = S
B = S2-
Which sphere (C or D) represents Li and which represents Li+?
C = Li+
D = Li
elements in the same group form ions of similar charge.
For metals in groups 1A, 2A, and 3A, the group number = what?
charge on the cation
- Group 1A elements have one V electron. Loss of this electron forms a cation with a +1 charge.*
- Group 2A elements have two V electrons. Loss of both electrons forms a cation with a +2 charge.*
All of the cations derived from group 1A-3A elements have an octet of outer shell electrons except for Li+ and Be2+. Li+ and Be2+ have a 1s2 electronic configuration like helium, the noble gas to which they are the closest.
These cations are especially stable because they have a filled outer shell of electrons, although they do not have an octet of electrons.
All of the cations derived from group 1A-3A elements have an octet of outer shell electrons except for Li+ and Be2+. Li+ and Be2+ have a 1s2 electronic configuration like helium, the noble gas to which they are the closest.
nonmetals form anions. For nonmetals in groups 5A, 6A, and 7A, the anion charge = what?
8 - (the group number)
Group 5A elements have five valence electrons. A gain of three electrons forms an anion with a -3 charge (anion charge = 8 - 5).
Use the group number to determine the charge on an ion derived from barium
from sulfur
Ba is in group 2A: Ba2+
S is in group 6A: S2-
The transition metals form cations (not so easy to predict)
Iron forms two different cations Fe2+ & Fe3+.
How are these formed?
Fe2+ is formed by losing two v electrons from 4s.
Fe3+ is formed by losing two from 4s & one from 3d
Why is the octet rule not usually followed with transition metals?
Transition metals generally have additional d electrons that the nearest noble gas does not.
Identify the ion
Co3+