Chapter 2: Elements are the building blocks of

matter.

Grade 9 ScienceUnit 1: Atoms, Elements, and

Compounds

ElementsA pure substance that cannot be broken down or separated into simpler substances.

Made up of one kind of atom.More than 115 elements known about 92 occur naturally.Bill Nye Video: Atoms and Elements

Chemical SymbolsOne or two (sometimes 3) letters used to represent an element name

Standard throughout the world

Examples: O = OxygenAu = Gold

Note:

Use Your Periodic Table on page 50 to Identify the Chemical Symbols of these 20 Need to Know Elements:

The Periodic TableOrganizes elements according to their physical and chemical properties.

Developed by Dmitri Mendeleev in 1867.

Includes the element’s name, symbol, atomic number and atomic mass.

ATOMIC NUMBER = # of Protons (& Electrons in a Neutral atom)

ATOMIC MASS = Average mass of the atoms of an element

MASS NUMBER= the number of Protons

+ the number of Neutrons

= The ROUNDED atomic Mass

To find the Number of Neutrons:

Subtract the Atomic number from the rounded Atomic Mass!

# Neutrons = 16 - 8 =8

Complete the Chart:Element Name

Symbol Atomic Number

# of Protons

# of Electrons

Atomic Mass

K

hydrogen

12

8

2

23.0

Text Page 51

Elements can be METALS, NON-METALS, or METALLOIDS

MetalsShinyMalleableDuctileUsually solid

Good conductors of heat and electricity

Non-metals

Tend to be gases or brittle solids

DullNot malleable or ductile

Poor conductors of heat and electricity

Metalloids

SolidsShiny or dullMay conduct electricity

Poor conductors of heat

Non-malleable and not ductile

Properties of both metals and non-metals.

The periodic table is organized into periods and chemical families.

Periods: the horizontal rowsFamilies: the vertical columns

Elements in the same family have similar physical and chemical properties.

See video clips on YouTube: Periodic Table of Videos

Chemical FamiliesAlkali Metals: Family 1

Highly reactive with halogens

Reactive with oxygen and water

Low melting points

Soft

Li, Na, K …

Video

Alkaline Earth Metals: Family 2

Less reactive then alkali metals

Burn in air if heated

Produce bright flames

React with water

Be, Mg, Ca…

Halogens: Family 17Non-metalsHighly reactive

F is the most reactive element

F, Cl, Br…

Noble Gases: Family 18

Very stable

Highly unreactive

All gasesHe, Ne, Ar…

Transition Metals

Found at the centre of the periodic table

Complex arrangement of electrons

Three are magnetic;

Fe, Co and Ni

Families of the Periodic Table

Questions page 59

#’s 1-14

Section 2.3 The Periodic Table and the Atomic Theory page 60

Bohr-Rutherford diagram

2e-8e-

8e-

18e-

Nucleus

Electron Filling Rules:- Use the ATOMIC NUMBER to determine the number of electrons and protons of the element- Levels are filled from the INNER most energy levels OUT.- The First Energy level can hold a MAXIMUM of 2 electrons- The second and third energy levels hold a MAXIMUM of 8 electrons

Energy Level Periodic Trends

1. The number of Valence Electrons = the Family Number2. The number of Energy Levels = the Period Number3. The Maximum Number of Electrons in each Level = the Number of

elements in that Period4. Elements in the same Family have the same number of Valence

Electrons

The valence shell of the noble gases is FULL; therefore stable.

Gaining or losing electrons will allow atoms to achieve a kind of stability. Metals will lose electrons while non-metals will gain them.

Questions Page 67#1-14