Do Now (In your Tracker)

Read the article and underline any words that you do not know. Answer the following questions: 1. What is the main idea of the essay? 2. What conclusion did the author reach?

How do you know? 3. How does this relate to science?

Today’s Lesson Topic: Atomic Numbers and Isotopes!

Class Updates

Tutoring will be on Thursday this week NOT Tuesday.

The price of hot chips is now 10 energy bars

If you need to take the quiz make sure you do so—tutoring would be a great opportunity to do so!

Today’s Objective:

SWBAT characterize and classify elements based on their atomic structure.

Essential Question: how can elements with different number of neutrons be similar?

Atomic Number (Z):

• is the number of protons in the nucleus of the atom. Z=#p• The number of protons (atomic number) determine the identity of an element.

What about the electrons? How many?

• Atoms have no overall electrical charge so, an atom must have as many electrons as there are protons in its nucleus. • # p =# e•The atomic number of an element also equals the number of electrons in a neutral atom of that element• Z =#e

Ex: Sodium

What is the atomic number of Sodium?

How many protons does sodium have?

How many electrons does sodium have? 11

11

11

Mass Number (A):

• The sum of the protons and neutrons in the nucleus.

A=#p + #n

Standard atomic Notation

Isotopes

They have different mass numbers

because they have

different numbers of neutrons,

but they have

the same atomic number because they have the same number of protons.

Atoms of the same element with

• Same number of protons

• Same number of electrons

• Different number of neutrons

Isotopes

Do isotopes have similar chemical properties? Why?

Yes – electrons are the same Do they have similar physical

properties? Why? NO – mass is different.

Example:Isotopes of Carbon and Hydrogen

protium deuterium tritium H H H

Isotopes of Carbon

Isotopes of Hydrogen

Atomic Mass Unit

is a unit used to compare

the masses of atoms

and has the symbol

u

or

amu.

1 amu or u

is approximately equal to

the mass of

a single

proton or neutron.

Carbon-12

Chemists have defined

the carbon-12 atom

as having a mass of

12 atomic mass units.

Atomic Mass

is the weighted average

mass

of all the naturally occurring

isotopes

of that element.

Exit Ticket:

Answer the following on your own piece of paper.

1. What does an atomic number of an element determine?

2.What is an isotope? 3. Write the number of protons,

neutrons and electrons for Carbon-12.