Introduction to Chemical Bonding Miss Elaine Macalinao Chemistry

Why form chemical bonds? Decrease potential energy Increase stability Chemical bond: a mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atom together Why form chemical bonds? Decrease potential energy Increase stability All atoms trying to achieve a stable octet Atoms unstable alone and lead more stable, happier lives when joined/bonded together with one or more other atoms Octet recall noble gases stability? ns2np6

Types of chemical bonding When atoms bond, their valence electrons are moved around in ways that make the atoms more stable The way their valence electrons move around determine the type of bond that happens 3 major types of chemical bonds: Ionic Covalent Metallic

Ionic Bonding Ionic bond: chemical bonding that results from the electrical attraction between large numbers of cations and anions Electrons are either gained or lost by an atom In doing so, both atoms often achieve the electron configuration of the nearest noble gas Occurs between metals losing electrons to nonmetals Very strong bond Other words: chemical bond in which one atoms loses an electron to form a positive ion and the other gains an electron to form a negative ion TRANSFER OF ELECTRONS! Ionic compounds = made up of atoms!

Ionic compound: composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal Most ionic compounds exist as crystalline solids 3D network of positive and negative ions mutually attracted to one another Ex: rocks, minerals

IONIC Definition Chemical bonding that results from the electrical attraction between large numbers of cations and anions Types of atoms involved Metals & nonmetals Method of bond formation Transfer of electrons Type of structure Crystal lattice Physical state Solid Melting point High Solubility in water Yes Electrical conductivity Other properties -- Image

Covalent Bonding Covalent bond: chemical bonding that results from the sharing of electron pairs between two atoms Neither atom has an electrical charge Forces between atoms are weak Bonding between atoms of the same elements is completely covalent

Molecule: a neutral group of atoms that are held together by covalent bonds Molecular compound: a chemical compound whose simplest units are molecules Diatomic molecule: a molecule containing only two atoms

COVALENT Definition Chemical bonding that results from the sharing of electron pairs between atoms Types of atoms involved Nonmetals Method of bond formation Sharing of electrons Type of structure Molecules Physical state Liquid or gas Melting point Low Solubility in water Usually not Electrical conductivity No Other properties Odorous Image

Metallic Bonding Metallic bonding: the chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons Within metals, vacant orbitals allow the atoms’ outer energy levels to overlap Result = electrons become delocalized Delocalized: not belonging to any one atom, but freely move about the metal’s network of empty atomic orbitals

De-excitation responsible for the shiny appearance of metal surfaces Metallic Properties High electrical and heat conductivity due to the freedom of electrons to move in a network of metals De-excitation responsible for the shiny appearance of metal surfaces - When light shines on these electrons, they vibrate and instead of energy springing from atom to atom it is reflected as visible light

Two important properties related to characteristics of metals: Malleability: the ability of a substance to be hammered or beaten into thin sheets Ductility: ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire Characteristics possible because metallic bonding is the same in all directions throughout the solid

METALLIC Definition Chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons Types of atoms involved Metals Method of bond formation Electrons are delocalized among metal atoms Type of structure “Sea of electrons” Physical state Solid Melting point Very high Solubility in water Yes Electrical conductivity Other properties Malleable, ductile, lustrous Image

Bond Polarity Most bonds are a blend of ionic and covalent characteristics Difference in electronegativity determines the bond type A large difference in electronegativity in a bond will result in ionic bonding A small difference between two atoms will results in covalent bonding

Non-polar covalent bond: a covalent bond in which the bonding electrons are shared equally by the bonded atoms, resulting in a balanced distribution of electrical charge Polar-covalent bond: a covalent bond in which the bonded atoms have an unequal attraction for shared electrons

Electronegativity Difference Bonding type How it looks like 0.0 – 0.3 Non-polar covalent 0.4 – 1.9 Polar covalent 2.0 – 3.3 Ionic Recall: Differences in electronegativities reflect the character of bonding between elements

Chemical Bonding Video

Show your understanding! Choose one of the following products to demonstrate what you have learned: Story – choose one type of bonding and write “A Day in the Life of an Atom” story describing your chosen bond type. The story should incorporate at least 5 properties from your Bonding Chart Comic Strip – Create a comic strip with 3+ frame for each bonding type. The comic should incorporate at least 3 properties from your Bonding Chart. Single-Frame Cartoon- Draw a single-frame cartoon for each type of bonding. Each cartoon should incorporate at least 2 key properties from your Bonding Chart. Essay – write a 5-paragraph essay comparing and contrasting each bonding type. The essay should incorporate the major properties from the Bonding Chart.