80 likes | 194 Vues
Understand how atoms gain, lose, or share electrons to form stable compounds like KI. Explore ionic bonds between metals and nonmetals, and covalent bonds where electrons are shared. Learn about single, double, and triple covalent bonds, as well as polar and nonpolar molecules.
E N D
Chapter 20 Section 2 Types of Bonds
Gain or Loss of Electrons • Atoms gain or lose electrons to achieve a stable energy level • Ion – a charged particle that has a different number of electrons than protons • Electrical forces between ions hold compounds together
A Bond Forms • A neutral K atom has 1 electron in its outer energy level (unstable) • K gives away its electron & becomes stable and positively charged (K+) • A neutral I atom has 7 electrons in its outer energy level (unstable) • I gains an electron to become stable and negatively charged (K-) • Oppositely charged ions attract each other and form the neutral compound KI • Superscripts (written above) are used to indicate ion charge
The Ionic Bond • Ionic bond – the force of attraction between opposite charges of ion in an ionic compound • Usually occurs between metals and nonmetals • There must be a net charge of zero (Mg2+ and 2 Cl-)
Sharing Electrons • Some atoms are unlikely to gain or lose electrons (Group 14) • These atoms become more chemically stable by sharing electrons • Covalent bond – attraction formed between atoms when they share electrons (nonmetals) • Molecule – a neutral particle that forms as a result of electron sharing
Single and Multiple Covalent Bonds • A single covalent bond is made up of 2 shared electrons (usually 1 from each atom in the bond) • Double bonds share 4 electrons (CO2) • Triple bonds share 6 electrons (N2)
Unequal Sharing • Electrons are not always shared evenly in a covalent bond • Related to size of the atom, charge of the nucleus, and total # of electrons • δ+ means partially positive and δ- means partially negative • Like tug of war! • Chlorine atoms attract electrons more strongly than hydrogen atoms do
Polar or Nonpolar? • Polar molecule – a molecule with a slightly positive and slightly negative end caused by unequal sharing • Overall, the molecule is neutral • Nonpolar molecule – a molecule that shares electrons equally and does not have oppositely charged ends • Molecules made of 2 identical atoms or perfectly symmetrical molecules