How do elements bond?
How do elements bond? Chemical bond – a force that holds two atoms together. Atoms form bonds with other atoms by using their outer electrons. Three types of chemical bonds: Ionic bond Covalent bond Metallic bond
Ionic Bonds Strong attraction between atoms that holds the atoms very close together. Electrons are gained or lost from an atom to form ions. Gain / Loss of electrons makes each atom STABLE!!!!
Ionic Bonds Chlorine Ion (Cl-) Chlorine (Cl) Sodium (Na) Sodium Ion (Na+)
Ionic Bonds Ex. Salt = Na + Cl Na Cl [Na]+ [Cl]- + +
Covalent Bonds When atoms don’t “want” to gain or lose outer level electrons, they must SHARE electrons to become stable. Covalent bond - Chemical bond formed from atoms sharing electrons. Molecule – Particle formed from atoms in a covalent bond. The smallest component of a compound that still has the properties of that compound. Pd 1, 2, 5
Covalent Bonds Ex. Hydrogen molecule = H + H H H H H +
Chemical Reactions Every chemical formula is made up of reactants and products. Reactants – “ingredients” that are needed to make something. Products – what is made Reactants make products
Chemical Formulas Reactant + reactant product + product Ice cream + banana + chocolate syrup + cherry + whip cream banana split Ex. Na + Cl NaCl sodium and chlorine makes sodium chloride Ex. O2 + C6H12O6 CO2 + H2O oxygen and glucose make carbon dioxide and water
CO2 + H2O H2CO3 Thermodynamics of a Chemical Reaction Bond energy is the amount of energy needed to break a bond between two atoms. Energy is added to break bonds. Energy is released after the bonds form. A reaction is balanced when the total bond energy of the reactants and is equal to the total energy in the products. CO2 + H2O H2CO3
Thermodynamics of a Chemical Reaction Exothermic reactions release more energy than they absorb. Reactants have higher bond energies than products. Excess energy is released by the reaction.
Thermodynamics of a Chemical Reaction Endothermic reactions absorb more energy than they release. Reactants have lower bond energies than products. Energy is absorbed by the reaction to make up the difference.