Science Unit 4 Test Review

Chemical Bonds

• Metal elements: donate electrons

• Nonmetal elements: accept electrons

• metal + nonmetal = ionic bond

• nonmetal + nonmetal = covalent bond

• metal +metal = metallic bond

during a reaction between a metal and a nonmetal atom, valence electrons are transferred and this is called an ionic bond.

Balancing Chemical Equations

• 3K + Cl₂ = 3KCl

• coefficient: 3

• subscript: 2

• reactants: 3K + Cl₂

• product: 3KCL

• matter is neither created or destroyed in a chemical reaction.

• after a reaction, the mass of the products is always equal to the mass of the reactants and such a reaction follows the law of Conservation of Mass

• during an endothermic reaction, heat is absorbed

• during an exothermic reaction, heat is released