LaunchGrab your binder and immediately take a seat

Place last night’s homework on your desk

Review answers with a partner and make corrections

How many particles?Mr. Heffner

9/17/09

How many particles?How do you find the # of protons in an atom?

Look at atomic number on the periodic table

Atomic number

5

BBoron

10.81

How many particles?How do you find the # of neutrons in an atom?

Look at atomic mass on the periodic tableCalculate: atomic mass – atomic number = #

neutrons

Atomic number

5

BBoron

10.81Atomic mass

How many particles?How do you find the # of electrons in an atom?

Look at atomic number on the periodic table# of protons = # of electrons

Atomic number

5

BBoron10.8

How many particlesExample #1: B (Boron)

# of protons?atomic number = 5therefore, B has 5 protons

# of neutrons?atomic mass = 11 (rounded up from 10.8) 11 – 5 = 6therefore, B has 6 neutrons

How many particles?# of electrons?

atomic number = 5# protons = # of electronstherefore, B has 5 electrons

How many particles?Let’s draw it!

# protons = 5# neutrons = 6# electrons = 5

How many particlesExample #2: Cl (Chlorine)

# of protons?atomic number = 17therefore, Cl has 17 protons

# of neutrons?atomic mass = 35 (rounded down from 35.45) 35 – 17 = 18therefore, Cl has 18 neutrons

How many particles?# of electrons?

atomic number = 17# protons = # of electronstherefore, Cl has 17 electrons

How many particles?Let’s draw it!

# protons = 17# neutrons = 18# electrons = 17

Exit Slip1. How many protons does Br have?

a. 17b. 35c. 79.9d. 80

2. How many neutrons does Mg have?a. 11.7b. 12c. 24d. 24.3

Exit Slip3. A valence ring/shell

a. is the innermost ring/shell where electrons are located

b. is the the outermost ring/shell where electrons are located

c. is the innermost ring/shell where neutrons are located

d. is the the outermost ring/shell where nuetrons are located

Exit Slip4. Which of the following correctly identifies the

number of particles in S (Sulfur)?a. 14 protons, 14 neutrons, 14 electrons

b. 16 protons, 15 neutrons, 16 electrons

c. 16 protons, 16 neutrons, 16 electrons

d. 16 protons, 16 neutrons, 17 electron

Exit Slip5. The following is a picture of an atom of what

element?a. B (Boron)

b. K (Potassium)

c. Pb (Lead)

d. C (Carbon)