Basic Chemistry
51
Occupies space
Has weight or mass
Matter
Can be broken down to elements
Smallest particles of an element
Atoms are neutral. # of protons = # of electrons
Atomic number
Atoms can vary in the number of neutrons they contain
Atoms
There are 92 naturally occurring elements
Compounds
Can not be broken down by chemical reactions
96% of body weight of living organisms made up of Oxygen, carbon, Hydrogen and Nitrogen
Elements
Is formed when two or more atoms chemically combine to form a single species.
Two covalently-bonded atoms will not share electrons equally.
Water
Ions and Polar molecules dissolve in water
Polar Molecules
Hydrogen bonds
Hydrogen bonds are weak
Molecules
Atoms react to give up, receive, or share electrons to produce a completed outer shell.
Atoms with incomplete shells react with others in a way that allows it to complete the outer shell.
Chemical bonds form when atoms react to fill their outer shells with electrons.
A compound is two or more elements joined together by chemical bonds.
Hydrogen bonds
The transfer of electrons enables the atoms to have complete outer shells.
This forms the crystals of salt we know
Ionic bonds
Ionic bonds are weak and can be easily separated in water
Bonding
Neutral pH = 7
Low pH (<7) = acids
High pH (>7) = bases
pH
Form when molecules are added to water and they lose a Hydrogen ion.
Acids produce hydrogen ions in water
Acids
Are substances that combine with hydrogen ions and reduce their concentration
Indirectly, NaOH reduces the amount of hydrogen ions
Bases
Neutral
Water - produces equal amounts of hyrogen and hyroxide ions
Chemical reactions
Basic Chemistry
All atoms of an element have the same atomic number
Smallest particles of an element
Substance made up of two or more elements
Ionic bonding occurs when electrons are transferred from one atom to another.
Extra electron transferred to the Chlorine atom
One electron in the outer shell
One electron MISSING in the outer shell
Sodium ion formed (+ve)
Chloride ion formed (-ve)
3.
The electrical attraction between sodium ions (+) and chloride ions (-) produces the regular arrangement diagramed below.
Chloride ion in green
Sodium ion in grey
Double and triple bonds
The attraction between water molecules and ions may be strong enough to separate the ions, causing the ions to become suspended (dissolved) in the water
1.
5.
Water is not an element
Oxygen and hydrogen are elements
Hydrogen bonds are weak
Covalent bonds form when atoms share electrons.
Below, two hydrogen atoms are bonded by a single covalent bond.
Hydrogen atoms contain one electron and one proton
The two atoms each share a pair of electrons.
Water molecules are also attracted to other polar substances causing them to adhere to many kinds of materials
Covalent bonds
Energy is required to form a covalent bond and energy is released when a Covalent bond is broken.
Molecules are two or more atoms that are held together by covalent bonds.
The partial positive charge on the hydrogen atoms in a molecule will be attracted to atoms with a negative charge.
Molecules may be composed of atoms of the same element or of different elements.
Simpler representation of methane
Forms a hydrogen bond
Even simpler: written as CH
4
Carbon needs four electrons, each hydrogen needs one
Each of the hydrogen atoms shares one electron with carbon
Unequal sharing of electrons results in the oxygen having a partial negative charge and the hydrogen atoms having a partial positive charge.
Shading is used in the drawing below to indicate the area of greatest electron density
In the drawing below, hydrogen shares one pair of electrons with chlorine by a single covalent bond
Hydrogen ion
It is showing three shells
Layer closest to nucleus has two electrons
Chloride ion
Electrons distributed around nucleus in layers called shells
The overall charge on the molecule is zero but chlorine has a partial negative charge and hydrogen has a partial positive charge
As a result of this, the chloride ion is more negative than the hydrogen ion, which is relatively more positive.
This is the aluminium atom
The molecule will be polar
Letters are used to represent atoms. The letters are called atomic symbols.
Electron shells
Measures the concentration of hydrogen ions
Symbols
Aluminium has three electrons in it's outer shell.
Fill inner layers first
Outer shell may not contain the maximum number of electrons
4.
The symbol for sodium is Na.
For example, the symbol for carbon is C.
It may contain up to eight electrons in this shell.
2.
Atoms
Called isotopes
Isotopes of hydrogen
Number of protons in an atom
6.
Neutrons
Particles with no charge found in nucleus
Protons
The partial positive charge on the hydrogen atoms in a molecule will be attracted to atoms with a negative charge.
Electrons in an atom better represented as a cloud
positively charged particles in nucleus of atom
Electrons
Particles with negative charge found outside of nucleus
Forms a hydrogen bond
positively charged particles in nucleus of atom
+
-
+
HCl
H
Cl
+
-
+
Na
OH
NaOH
-
+
O
H
OH
+
H
2