Fundamental Ideas Chemistry 1

Nota:

• Key Points 1. All substances are made of atom

1. All substances are made of atoms
2. Elements are made of only one type of atom
3. Elements in the same group of the periodic table often have similar properties
4. Compounds are formed when two or more electrons are combined together

1. The nucleus of an atom is made of protons and neutrons
2. Protons have a positive charge Electrons have a negative charge Neutrons are not charged
3. The atomic number of an element is equal to the number of protons in the nucleus of its atoms
4. Elements are arranged in order to their atomic numbers in the periodic table
5. The mass number is the sum of the protons and neutrons in the nucleus of an atom

1. The first shell can hold up to two electrons and the second can hold eight
2. All the elements in the same group of the periodic table have the same number of electrons in their highest energy level
3. Electrons occupy the lowest energy levels first

1. Compounds of metals bonded to non-metals have ionic bonds
   1. When a metal reacts with a non-metal, ions are formed. Metal atoms lose one or more electrons to form positively charged ions. Non-metal atoms gain electrons to form negatively charged ions. The oppositely charged ions attract each other strongly and the compound has ionic bonds.
2. Compounds of non-metals have covalent bonds