Chemistry Chapter 5

Noble gases
These don’t combine with other atoms
Pure substance, composed of two or more elements with a definite composition
Compound
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Ionic or covalent
2 types of compounds
One or more electrons are transferred from the atoms of metals to atoms of nonmetals
Ionic compound (what happens with electrons?)
The cations and anions have different charges and are attracted to each other. They do not actually share electrons.
Explain ionic bonds
Ionic bond
Transfers of electrons from metals to nonmetals forms what type of bond?
Cations (positive charge)
Anions (negative charge)
Transfers of electrons from metals to nonmetals form what?
When atoms share one or more valence electrons.
Explain covalent bonds
There are more covalent compounds. Simple covalent compounds are present in everyday lives.
Are there more covalent compounds or ionic ones?
-Compound is a pure substance of two or more elements.
-Bond is how atoms stay together.
Bond vs. compound
To make stable electron configurations. Octet rule.
Why do compounds form?
-When atoms lose or gain electrons
-Get an electoral charge
(more electrons than protons, negative charge…less electrons than protons, positive charge)
Ions
How easy it is to remove a valence electron. (Increases left to to right because noble gases are stable…increases going down rows because more shells appear so electrons are further from nucleus)
Ionization energy
1+ (cations) 1- (anions)
Ionic charges
Metal, non-metal
Cations, anions
Order of ionic bonds
Lose
Metals and valence electrons
Gain
Non metals and valence electrons
The group number indicates the number of valence electrons an element must gain or lose in order to form a stable electron configuration and form an ionic compound.
How does group number correspond to valence electrons?
Is high because they Ionic bonds are strong
Melting point of ionic compounds
Is ALWAYS 0
Sum of charges in ionic compounds
Group of ions that has the lowest ratio of ions in an ionic compound
Formula unit
A metal (forms cation) and non metal (forms anion)
Ionic compounds form between?
Name metal, then take first syllable of the nonmetal and add “ide”
How do you name an ionic compound
more than one positive ion
Transition metals form…
Add a roman numeral of the positive charge in parenthesis. Example Fe2+ is Fe(II)
Writing ions of transition metals
Group of covalently bonded atoms with an overall ionic charge.
What is a polyatomic ion?
1-, 2-, or 3-
This indicates 1, 2, or 3, electrons were gained.
Most polyatomic ions have what charges? What does this imply?
-ate or -ite
Most polyatomic ions end in what?
Second, they act as the anion.
Where do polyatomic ions go in an ionic compound?
Covalent
Nonmetals form what kind of compounds?
Because they have high ionization energy, so it takes a lot of energy to lose an electron.
Why do nonmetals form covalent compounds?
A covalent bond forms.
When nonmetals share electrons what happens?
A molecule
When two or more atoms share electrons, what is formed?
The protons attract the electrons of another atom. This pull is stronger than the electrons going against each other. They get closer until a covalent bond is formed.
Nucleus and electron connection in covalent bonds.
bonding pairs (in-between two atoms that are covalently bonded)
Shared electrons are also called
A straight line
In Lewis dot structures, a covalent bond is represented by?
Two like atoms.
Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, Iodide
Diatomic
2 pairs of electrons are shared
Double bond
3 pairs of electrons are shared
Triple bond
All of the possible multiple electron-dot structures. Represented with an arrow
Resonance structures
First non-metal, uses element name
Second non-metal, first syllable of element name and -ide
Subscripts indicating more than 1 atom: use pre-fix
Naming covalent compounds
mono, di, tri, tetra, penta, hexa
Prefixes
Is usually omitted
Mono
Prefixes
The ability of an atom to attract the shared electrons in a chemical bond
Electronegativity
Non metals, because they have a high attraction for electrons
Nonmetals or metals have a higher electronegativity?
A covalent bond between atoms with identical or very similar electronegativity values. Symmetrical electron cloud around atoms
Non-polar covalent bond
A covalent bond between atoms with differ electronegativity values. The electrons are share unequally. The cloud in unsymmetrical
Polar covalent bond
Increases going across
Decreases going down
Electronegativity trends
it’s electronegativity difference
The polarity of a bond depends on…
More attracted to the more electronegative bond. So some of the electrons move that way. This makes one side more positive and the other more negative.
In a polar covalent bond electrons are…
with a bigger difference in electronegativity
A bond becomes more polar…
A polar covalent bond with a with a separation of charges
Dipole
0.0-0.4
Range of electronegativity difference considered Non-polar covalent
0.5-1.8
Range of electronegativity difference considered Polar covalent
electrons are transferred from one atom to the other to form an ionic bond
When the electronegativity difference is greater than 1.8
Electron groups rearranged as far apart as possible to minimize the repulsion between them. The specific shape of the molecule is determined from the number of atoms attached to the central atom.
VSEPR theory
The bonds (single, double, or triple that hold atoms together)
Electron groups
-Solid at room temperature
-Form crystals instead of molecules
-High melting and boiling points
-Are neutral
-Metal then non-metal
Properties of ionic bonds
Only 2 electrons
Stable He valence electron
Single bond. Why? Because the other shells are full, there’s only one valence electron to share with.
Group 7A elements can only form what type of bond?
Single or double.
Group 6A elements can form what types of bonds?
Single, double, or triple.
Group 5A elements can form which types of bonds?
Leaset electronegative first.
Order of atoms in a covalent compound.
Occur between polar molecules. Partially positive charge of one molecule is attracted to the partially negative charge of the other.
Dipole-dipole attractions
Strongest dipole-dipole attraction.
Partially positive hydrogen atom and lone pair of nitrogen, oxygen, or fluorine.
Hydrogen bond
Non-polar molecules. Occur if electrons accumulate unequally, form a temporary dipole. Typically weak, still allow non polar molecules to form liquids and solids.
Dispersion forces
strongest: hydrogen bonds
next: dipole-dipole interactions
least: dispersion forces
Attractive forces/bonds between molecules (in order of strength)
Strength of the attractive forces between its particles.
The melting point of a substance is related to the
low
Compounds with dispersion forces will have a _____ boiling/melting point
higher
Compounds with hydrogen bonds or dipole dipole interactions will have a ______ higher boiling/melting point
-the electron groups around a central atom
-are arranged as far apart from each other as possible
-have the least amount of repulsion of the negatively charged electrons
-have a geometry around the central atom that determines molecular shape.
VSEPR (valence shell, electron pari repulsion)
Could be regular 2 atoms:
-Polar: electrons unequally distributed and dipole formed
-Non-polar: symmetrical distribution of elections, equal electronegativity

IF NOT

Look for which atom is the most electronegative. The dipole arrow points that way. If the arrows point away from central atom is is non polar because the dipoles cancel the polarization.

If the dipole arrows point towards the central atom, it is polar.

Steps to determine if a molecule is polar or non-polar.
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