chemistry for biologists

What three particles are atoms made up of

Proton , neutron , electron

Neutron

No charge but have mass, found in the nucleus

Proton

Have positive charge and same mass as neutrons, found in nucleus

Electron

Have negative charge, a mass of 1/1836 that of a proton. Found in all the space surrounding the nucleus

Atomic number

Z= number of protons in the nucleus

For a neutral atom, also the number of electrons orbiting the nucleus

Mass number

A= the number of protons + neutrons in the nucleus

Octet rule

During a chemical reaction, an element will try to attain the same number of electrons as a noble gas. Atoms try to gain, lose or share electrons in order to haven the same number of electrons as a noble gas

What controls the chemical and physical properties

The distribution of electrons within the levels and sub levels

Paulis exclusion principle

In an atom or molecule, no two electrons can have the same four electronic quantum numbers

n

Principle energy level

l

Sub shell

ml

Orbital

ms

Spin

Principle energy level

Each principle energy level ( or electron shell) has a fixed maximum number of electrons it can hold

Energy sub-shells: secondary quantum number

Also known as orbital, angular or azimuthal quantum number

Shells are subdivided into subshells. The number of subshells within each shell is the principle energy level of that shell

Atomic orbital

Region in space where the probability of finding an electron is highest

The subshells are divided into atomic orbitals. Each atomic orbital can hold 2 electrons. Each electron in the pair must have opposite spin

Modern periodic table

Arranged in order of increasing atomic number

Vertical columns are called groups, elements in a row exhibit trends in chemical reactivity

Horizontal rows are called periods

There are 4 blocks based on where the elements outer electrons lie

Looking at an electrons position can tell you about its chemical and physical properties

S orbitals

Shaped like a sphere, there is one s orbital within the s subshell

It can hold 2 electrons

P orbitals

Dumbbell shaped

In the p subshell there are 3p orbitals of equal energy