2 A chemical bond is a force that holds atoms together.
3 Two Types of Bonds Ionic Bond – the attraction between two oppositely charged ions An ionic bond is formed when atoms gain or lose electrons. Ionic bonds form compounds.
4 Ion – an atom or group of atoms that has become electrically charged Ion – an atom or group of atoms that has become electrically charged. It is a charged particle. When an atom loses an electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.
9 Compound – two or more elements chemically combined by gaining, losing, or sharing electrons. Molecule – a particle made of 2 or more atoms covalently bonded together.
10 Chemical formulas – a shorthand way to represent a compound Chemical formulas – a shorthand way to represent a compound. ( H2O) In a chemical formula, the element with the positive charge is always written first.
11 Valence number – The number of electrons an atom needs to gain, lose, or share to become stable. (Gain electrons – negative valence) (Lose electrons – positive valence.)
12 Subscript – the number that shows how many atoms of an element are in the compound.
13 How to Write Formulas 1. Write the symbol correctly for both elements. 2. Write the valence number above each symbol. Make sure you have a positive first, and then a negative.3. Criss-cross valences to make a subscript.4. NEVER write 1 as a subscript. (It is understood to be 1 if there is no number.)5. Reduce to lowest terms.
17 Binary Compound – a compound composed of 2 elements Binary Compound – a compound composed of 2 elements. Polyatomic Ion- a group of positively or negatively charged covalently bonded atoms.
18 Calcium Phosphate Tin (IV) Chromate Ammonium Oxide Magnesium Sulfate
19 Naming compounds – change the ending of the second element to – “ide” Naming compounds – change the ending of the second element to – “ide”. (Do not change the names of polyatomic ions.) Check to see if Roman numeral is needed. Ex: NaCl - Sodium Chloride Fe2O3 – Iron (III) Oxide