Chem chapter 3: chemical bonds

compounds

elements can form this; atoms of 2 or more elements are chemically linked to one another

• group 8A elements (noble gases) are the exception bccause they have 8 valence electrons

octet rule

the tendency of atoms to have eight valence electrons when they form molecules or ions; representative ions tend to do this; each atom in compound has 8 electrons in outermost shell

chemical bond

an attractive force that holds atoms together in a chemical compound

bonding electron pair

pair of electrons shared by 2 atoms and holds the atoms close to each other

covalent bond

a chemical bond that is formed by sharing

molecule

a group of two or more of same or different atoms linked by covalent bonds

compound

combo of 2 or more different elements

nonbonding electron pairs

pair of valence electrons that is not shared with another atom

elements with 3 or less VE

do not normally form covalent bonds but can form ionic compounds to satisfy the octet rule

key concepts

1. elements in groups 4A through 7A can satisfy the octet rule by sharing electrons with one another

2. the number of covalent bonds an atom makes equals the number of empty spaces in the valance shell of an atom

3. atom that forms the most bonds go in center of molecule 

single bonds

when 2 atoms share one pair of electrons

double bonds

a covalent bond where 4 electrons (two pairs) are shared between 2 atoms

triple bond

a covalent bond in which 6 electrons (3 pairs) are shared between 2 atoms

polar covalent bond

bond where the bonding electrons are shared unequally, giving one atom a positive charge and the other a negative charge

non polar covalent bond

bond where neither atom has an electrical charge

electronegativity

the attraction of an element for electrons

high electronegativity

element has strong attraction for elements

low electronegativity

element has weak attraction for elements

left to right

electronegativity increases from left to right; group 1A elements have weakest attraction and group 7A has strongest

bottom to top

electronegativity increases from bottom to top

AT has 2.2 electronegativity to fluorine at 4.0 within group 7

binary compounds

compounds made from 2 elements

1. write the name of the element that has the lower electronegativity first

2. write the name of the other element using modified names that end with suffix ide

3. add prefixes to tell how many atoms of each element are present 

prefixes for # of atoms in covalent compounds

1. mono (mon)

2. di

3. tri

4. tetra (tetr)

5. penta (pent)

6. hexa (hex)

> 4 valence electrons

atoms with fewer than 4 valence electrons satisfy the octet rule by losing electrons to form ion

ion