Chemistry Review

Do you remember anything from science investigations?

Atomic Structure

Nucleus- center of an atom -contains protons - which are positive -contains neutrons- which are neutral Electrons (which are negative) surround the

nucleus in energy levels 1st energy level = holds 2e 2nd energy level = holds 8e 3rd energy level = holds 18e 4th energy level = holds 32e

Bohr Model of Atom

Periodic Table tidbits

Period table organization – organized by increasing atomic number

Split into metals (left side of stair step line) and nonmetals (right side of stair step line)

Groups – vertical columns (#1-18) Periods – horizontal rows (#1-7)

More Chemistry tidbits Atomic number = number of protons Mass number = # protons + # neutrons #Neutrons = mass number - # protons # protons = # electrons REMEMBER “APE”= ATOMIC NUMBER,

#PROTONS, #ELECTRONS WILL EQUAL EACH OTHER IN A NEUTRAL ATOM

Isotopes (I said isotope you dope!)

Isotopes are different atoms of the same element that contain the same number of protons but different number of neutrons.

Examples Cl-35 vs. Cl-37 17P 17P 18N 20N

Chemical Bonding Remember atoms bond with one another

in order to become stable (need to get 8 electrons in outer ring)

Exception- hydrogen only needs 2 electrons in outer ring to be stable

Bonds are forces of attraction between elements

Involves bonding of valence electrons (electrons in outermost shell)

Lewis Dot Structures

Lewis dot diagrams- display the number of valence electrons (outermost electrons) around the element symbol

Used to show how atoms of different elements bond and form compounds

Hint- use group number to find valence electrons

Electron configurations

Lewis Dot Diagrams

Types of Bonds

Covalent bond – sharing of electrons

-occurs between 2 nonmetals

-types- single (shares 1 e)

double (shares 2 e)

triple (shares 3 e)

*REMEMBER HYDROGEN IS A NONMETAL AND FORMS COVALENT BONDS!!!

Covalent bonds

H2-hydrogen gas-sharing of electrons

Types of Bonds

Ionic bond- one atom gives an electron to another atom (remember it’s the losing and gaining of electrons)

Involves forming ions (have positive and negative charges)

Occurs between a metal and a nonmetal

Bond Diagrams

Covalent bonds-remember they share electrons

Ex. F2

Bond Diagrams

Ionic Bond-

-lose & gain

electrons Ex. NaCl

Ionic bond Lewis dot diagram

NaCl- sodium chloride

Covalent Bond Lewis dot structure

HF-hydrogen fluoride

What is inside the nucleus of an atom?

1. Protons and electrons

2. Electrons and neutrons

3. Protons only

4. Protons and neutrons

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What are the dots in Lewis dot diagrams?1. Number of protons

2. Number of neutrons

3. Number of valence electrons

4. Number of inner shell electrons

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An ionic bond is between 1. 1 metal and 1

nonmetal

2. 2 nonmetals

3. 2 metals

4. None of the above

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A covalent bond is between

1. 2 metals

2. 1 metal and 1 nonmetal

3. 2 nonmetals

4. 3 metals

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How do you find the number of valence electrons to draw for a Lewis dot diagram

1. Look at the atomic number

2. Look at the mass number

3. Look at the number of neutrons

4. Look at the group number

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