Chemical Bonding When two or more atoms join a bond is formed It will not fall apart unless enough energy is added to break the bond The type of bond determines certain properties of the compounds they create
Why do atoms bond? Octet Rule: Atoms tend to gain, lose, or share electrons so as to have 8 electrons in their outermost shell (except for H and He)
Types of Bonds There are three main types of bonds: Ionic Bond Covalent Bond Metallic Bond
Learning Check: When two or more atoms join, a _________ forms. Bond How many electrons do most atoms want in their outer shells? 8 What are the three types of bonds? Ionic, Covalent, and Metallic
IONIC BOND bond formed between two ions by the transfer of electrons
Ionic Bonds Form between metals and nonmetals Involves the transfer of electrons The metal gives away electron(s) becoming a positive ion The nonmetal gains electron(s) becoming a negative ion The charged atoms are held together because the positive and negative forces are attracted to one another
Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl- ), charged particles or ions.
Properties of Ionic Bonds Network solids High melting and boiling points Conduct electricity when melted Many soluble in water but not in nonpolar liquid
Learning Check: When a bond is formed by the transfer of electrons, a __________ bond is formed. Ionic These bonds form between… Metals and nonmetals The metals lose electrons to the nonmetals to create positive and negative ________. Ions
COVALENT BOND bond formed by the sharing of electrons
Covalent Bonds Form between nonmetals Involves the sharing of electrons The nonmetals share one or more pairs of electrons to have a full octet Two types: polar and nonpolar
Two Types: Determined by how electrons are shared Based on electronegativity Shared evenly = Nonpolar Shared unevenly = Polar
Non polar Covalent Bonds when electrons are shared equally H 2 or Cl 2 Oxygen Atom Oxygen Molecule (O 2 ) Oxygen Molecule (O 2 )
Nonpolar Covalent Bonds: Evenly matched, but willing to share.
Polar Covalent Bonds when electrons are shared but shared unequally H 2 O
Polar Covalent Bonds: Unevenly matched, but willing to share.
Properties of Covalent Bonds Gases, liquids, or solids Low melting and boiling points Poor electrical conductors in all phases Many soluble in nonpolar liquids but not in water
Learning Check: When a bond is formed by the sharing of electrons, a __________ bond is formed. Covalent These bonds form between… Nonmetals When atoms have different electronegativities, and share electrons unevenly, a ________ molecule is formed. Polar
METALLIC BOND bond found in metals; holds metal atoms together very strongly
Metallic Bonds Form between metals Involves the overlapping of outer energy levels Attraction between one atom’s nucleus and a neighboring atom's electrons packs the atoms closely together Allows electrons to move freely from one atom to another.
Metallic Bonds: Mellow dogs with plenty of bones to go around.
Properties of Metallic Bonds Form alloys Examples: steel, brass, bronze and pewter Metals conduct electricity well do to the freedom of the electrons to move. Metals are flexible because the atoms can slide past each other without their bonds breaking.
Identifying Types of Bonds 1. Look at the chemical formula 2. Identify the elements in the compound 3. Determine if the elements are metals or nonmetals (using a periodic table) 4. Metal – Metal = Metallic 5. Metal – Nonmetal = Ionic 6. Nonmetal -- Nonmetal = Covalent 1. Polar Covalent = different atoms/elements 2. Nonpolar Covalent = same atoms/elements
Remember: Metals are on the left of the periodic table, and nonmetals are on the right.
Learning Check: Identify the type of bond present in each compound: CH 4 ○ Carbon = Nonmetal ○ Hydrogen = Nonmetal ○ Covalent Bond (polar) LiBr ○ Lithium = Metal ○ Bromine = Nonmetal ○ Ionic Bond FeCl 3 ○ Iron = Metal ○ Chlorine = Nonmetal ○ Ionic Bond O 2 ○ Oxygen = Nonmetal ○ Covalent Bond (nonpolar )
Polyatomic Ions Compounds that contain polyatomic ions contain both ionic and covalent bonds Involves groups of covalently bonded atoms that have either lost or gained electrons. Parenthesis group the atoms of a polyatomic ion to remind you that they act as one ion. Pg. 158 contains a list of many common Polyatomic Ions.
Learning Check: Identify the type of bond present in each compound: MgCl 2 ○ Magnesium = Metal ○ Chlorine = Nonmetal ○ Ionic Bond NH 4 Cl ○ Ammonium = Polyatomic Ion ○ Chlorine = Nonmetal ○ Both; Ionic and Covalent NaOH ○ Sodium = Metal ○ Hydroxide = Polyatomic Ion ○ Both; Ionic and Covalent NO 2 ○ Nitrogen = Nonmetal ○ Oxygen = Nonmetal ○ Covalent Bond (polar )