LECTURE 3 4 LEWIS STRUCTURES What are the

LECTURE 3. 4 – LEWIS STRUCTURES

What are the types of ions that can form?

I. Ions • When atoms gain/lose electrons, they gain a charge. • Ion – An charged atom due to unequal number of protons and electrons • Cation – A positively charged ion • Anion – A negatively charged ion

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+1 0 +2 +3 ± 4 -3 -2 -1

How do you draw Lewis Structures?

I. Lewis Dot Structures • Bohr diagrams take too long to draw • Lewis Dot structures only show the valence electrons. • Group number (Group 1 A, 2 A, etc. ) tells us the number of valence electrons

Class Example • Draw the Lewis structure for fluorine

Table Talk • Draw the Lewis Structure for Carbon

Stop and Jot • Draw the Lewis structure for Mg. What would the charge of a magnesium ion after the Octet Rule?

How do you show electrons being shared?

Lewis Structures for Ionic Bonds Na Cl

Lewis Structures for Ionic Bonds + [Na] [Cl]

Chemical Bonding Ionic Bonds Metallic Bonds Covalent Bonds

I. Covalent Bonding • This is a bond between only non-metals. • In a covalent bond, the electrons are shared between the elements so that each can get an Octet. • Most molecules in biology are covalent compounds

II. Drawing Lewis Structures • Halogens and hydrogen form only one bond are located at the end of a molecule. • The central atom is always carbon (if it is present) and/or the element that has the lowest electronegativity.

Class Example • Draw the Lewis structure for H 2 S

Table Talk • Draw the structure for NH 3

Stop and Jot • Draw the Lewis structure for C 2 H 6

III. Single, Double and Triple Bonds • Elements can share more then one set of electrons. • Also can form double and triple bonds. • Single bond = 2 electrons • Double bond = 4 electrons • Triple bond = 6 electrons

Class Example • Draw the Lewis Structure for CH 2 O

Table Talk • With your table, draw the structure of C 2 H 2

Stop and Jot • Draw the structure of HCN