Atoms Review

Some Definitions

• Atom – smallest unit of an element that maintains the chemical properties of that element

• Three subatomic particles –– Protons – positively charged particles in the nucleus of

an atom– Neutrons – neutrally charged particles in the nucleus of

an atom– Electrons – negatively charged particles orbiting an

atom

Elements in the Periodic Table

• Draw the carbon box from the board and label the atomic number, atomic mass, symbol

Some Questions

• What do atoms of an element have in common with other atoms of the same element?

• Why do unreactive atoms have no overall charge?

Another Definition

• Isotopes – Atom that has the same number of protons but a different number of neutrons. This causes the mass of the element to vary.

• Example – 3 Hydrogen isotopes – protium, deuterium, and

tritium– Radioiosotopes and medicine

Quick Lab – Modeling Isotopes

• Materials:– 3 different colored beads– Piece of paper– Writing utensil

1. Create atomic models for the three isotopes of hydrogen (see board)

Check with Ms. B

2. Create atomic models for the two isotopes of helium (see board)

Check with Ms. B

Questions

• How do the isotopes of hydrogen compare to one another?

• How do the hydrogen isotopes differ from the helium isotopes?

• Which isotopes have the same mass number? Which isotopes have the same atomic number?

Electrons

• “In the modern atomic model, electrons can be found only in certain energy levels, not between levels.”

• Fast moving in orbitals• Orbitals: region in an atom where there is a

high probability of finding electrons• The number of energy levels that are filled

depends on the number of electrons

Electron Energy Levels

• Animation of Electrons in Energy Levels• Let’s make another visual: Another Bead Lab– After getting a paper from Ms. B, place 2 beads(aka.

Electrons) in each open square and record in your own notes, how many electrons can fit in each energy level

– Draw a model (nucleus in center and energy levels surrounding the nucleus) of atoms for atomic number 3, 5, 10, and 20. Use your table with pennies to help you determine how many electrons go in each energy level. See board for atomic numbers and mass numbers.

Valence Electrons

• Valence Electrons are the electrons in the outer most energy level of an atom.

• They determine the chemical properties of an atom/element

• How many valence electrons are in the models you made? (atomic numbers: 3, 5, 10, 20)

Dot Diagrams

• Dot Diagrams show how many valence electrons an atom has.

• Let’s Look at how this is done (Handout)

• Record the pattern from the board in your notes

The Periodic Table

• Arranged by Atomic Number• An __________ is the basic form of matter

that cannot be chemically changed or broken down into anything simpler.

• Elements with shared characteristics are in the same column or _______________.

• Rows of the periodic table are called _______________.

More about the Periodic Table

• The metals are located on the _______________

• The non-metals are located _______________• The elements that are located between the

metals and the non-metals are known as ________________________.

Periodic Table and Electrons

• We already know how to find the number of valence electrons, but let’s review.

• Group 1 has ___ valence electrons• Group 2 has ___• Group 13 has ___• Group 14 has ___• Group 15 has ___• Group 16 has ___• Group 17 has ___• Group 18 has ___ (This group is inert – non-reactive and is

known as the Nobel Gases.)

The Octet Rule

• ______ electrons in the outer shell (thus filling up the s and p orbitals {remember there is 1 s orbital and 3 p orbitals so this is a total of 4 orbitals that can hold two electrons each so therefore 8 electrons fills them up!})

• atoms tend to ______, ______ or ______ electrons so as to have eight electrons in their outer electron shell.

• Lewis dot structures help us to see how many electrons an atom needs to gain, lose or share

Non-Metals like to gain electrons

• Draw a Lewis Dot structure for each of the following elements

• H, C, N, O, Cl, Si, P, S, Br

• Look at the Lewis dot structures you drew and determine how many electrons each atom would like to gain.

Non-Metals gain electrons

• Electrons to be gained by ... • H, C, N, O, Cl, Si, P, S, Br • 1, 4, 3, 2, 1, 4, 3, 2, 1

Ions

• ______ are charged atoms.• They gain a charge by either gaining or losing

_______________.• An atom that has ______ electrons than protons will have a

____________ charge.• An atom with a negative charge is called an ____________.

___________gain electrons, so they are anions• An atom that has ______ electrons than protons will have a

____________.• An atom with a positive charge is called a _____________.

Metals lose electrons so they are _____________.

How do we find the charge?

• Subtract the number of electrons from protons. If the number is positive then it is a positive ion, if the number is negative then it is a negative ion.

• Let’s practice with a couple.

• Cl, Mg, I, Na

Ion Notation

• How do we indicate whether an atom is an ion?? • Use notation

• Cl 1- , Mg2+

• So, since Cl says 1- it means that it has 1 extra electron than it would if it was a neutral atom, so how many electrons will it have?

• Since Mg says 2+, it means that it has 2 less electrons than it would if it was a neutral atom, so how many electrons will it have?

• Homework Practice!