A MATTER OF FACT

Introduction to Elements, Atoms, and the Periodic Table

WHY ISN’T IT A GOOD IDEA TO CLASSIFY MATTER BY ITS PHASES?

Because one kind of substance can exist in more than one phase (such as H20 can be ice, water, or steam) and matter changes phases rather easily.

WHY ISN’T MATTER CLASSIFIED ACCORDING TO ITS PHYSICAL CHARACTERISTICS, SUCH AS COLOR?

Scientists would not find it very useful to group sunflowers, gold, and the sun together.

ELEMENTS, COMPOUNDS, & MIXTURES

Scientists like to classify things. One way that scientists classify matter is

by its composition (what it’s made of) All matter can be classified as one of three

categories: elements elements compoundscompounds mixturesmixtures

ELEMENTS Elements are the simplest pure

substances. An element cannot be broken down or

separated into simpler substances by physical or chemical means.

Elements are the building blocks of all materials. About one hundred elements can combine in

different ways to form millions and millions of different substances!

ELEMENTS AND ATOMS

Elements are made of particles. Elements are pure substances.

All of the particles that make up an element are exactly alike.

The smallest particle into which an element can be divided and still be the same substance is called an…

Atom

PARTS OF THE ATOM Atoms are made of three

different types of particles: Proton – Positively charged (+) Neutron – No charge (neutral) Electron – Negatively charged

(-)

Nucleus – Center of the atom Made of protons and neutrons

Electrons are constantly moving around the nucleus.

PARTS OF THE ATOM

ELEMENTS AND THEIR SYMBOLS

In 1813, a system of symbols representing the elements was introduced. Each symbol consists of one or two letters. Two letters are needed for a chemical symbol when the first letter of that element’s name has already been used.

COMMON ELEMENTSAluminumAluminum AlAl

BromineBromine BrBr

CalciumCalcium CaCa

CarbonCarbon CC

GoldGold AuAu

HeliumHelium HeHe

HydrogenHydrogen HH

NitrogenNitrogen NN

PERIODIC TABLE

CLASSES OF ELEMENTS Metals

Most of the elements on the periodic table are metals. Metals tend to be solids that are shiny, malleable, ductile,

and good conductors of electricity.

Nonmetals More than half of the nonmetals are gases. Nonmetals typically are not shiny, not malleable, not ductile,

and are poor conductors of electricity.

Metalloids Metalloids are also known as semiconductors. Metalloids have some properties of metals and some of

nonmetals.