Valence Electrons & Bohr Diagrams

Atomic Structure Atoms have a nucleus that contains Protons and Neutrons Electrons are contained in shells that surround the nucleus An atom is made of mostly empty space Protons have a positive charge Electrons have a negative charge Neutrons are Neutral

Valence Electrons Electron Shell Number of Electrons 1 2 8 3 4 18 5 6 Each electron shell can hold a certain number of electrons Electron shells are filled from the inside out Noble Gases have full outer electron shells All other elements have partially filled outer electron shells Electron Shell Number of Electrons 1 2 8 3 4 18 5 6 32 7

Valence Electrons The electrons in the outer most electron shell are called valence electrons The shell containing electrons that is furthest from the nucleus is called the valence shell The number of electron shells with electrons is the same as the period number

Noble Gas Stability Noble gases are usually unreactive This is because they have full valence shells An element with a full valence shell is a happy element  For two atoms to join together atoms must gain, lose or share electrons Elements with full valence shells do not easily gain or lose electrons

Noble Gas Stability Atoms want to gain stability Atoms will try to gain or lose electrons to have a full valence shell Metals try to lose electrons Non-Metals try to gain electrons

Becoming An Ion Electrons are negatively charged Protons are positively charged Neutral atoms do not have a charge because the number of protons is the same as the number of electrons When atoms gain or lose electrons they become positively or negatively charged An atom with a charge is called an Ion

Bohr Models Niels Bohr created a visual model of the atom to make them easy to understand A Bohr Model contains a central nucleus surrounded by electron shells For each model you state the number of protons and neutrons in the nucleus and draw a dot on the electron shells for each electron