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Elements and the Periodic

Table

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Classification is arranging items into groups

or categories according to some criteria.

The act of classifying creates a pattern that

helps you recognize and understand the

behavior of fish, chemicals, or any matter in

your surroundings.

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These fish, for

example, are

classified as

salmon because

they live in the

northern Pacific

Ocean, havepinkish colored

flesh, and

characteristicallyswim from salt to

fresh water to

spawn.

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Classifying Matter

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Matter is usually defined as anything that has mass

and occupies space. Metals and Nonmetals

A metal had the following properties.

Metallic luster High heat and electrical conductivity.

Malleability, able to be rolled or pounded into a thin sheet.

Ductile, can be pulled into a wire.

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A nonmetal has the following properties

No metallic luster

Poor conductor of heat and electricity.

When it is a solid it is brittle so it cannot be poundedor pulled into a wire.

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Solids, Liquids, and Gases

Gases have no defined shape or defined volume

Low density

Liquids flow and can be poured from one container to

another Indefinite shape and takes on the shape of the container.

Solids have a definite volume

Have a definite shape.

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(A)A gas dispenses throughout a container, taking the shape

and volume of the container. (B) A liquid takes the shape of

the container but retains its own volume. (C) A solid retains

its own shape and volume.

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Mixtures and Pure Substances

A mixturehas unlike parts and a composition that varies

from sample to sample

A heterogeneous mixture has physically distinct parts

with different properties.A homogeneous mixture is the same throughout the

sample

Pure substances are substances with a fixed composition

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A classification scheme for matter.

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A physical change is a change that does not alter the

identity of the matter.

A chemical change is a change that does alter the

identity of the matter.

A compound is a pure substance that can be decomposed

by a chemical change into simpler substances with afixed mass ratio

An element is a pure substance which cannot be broken

down into anything simpler by either physical or

chemical means.

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Sugar (A) is a compound that can be easilydecomposed to simpler substances by heating. (B)One of the simpler substances is the black elementcarbon, which cannot be further decomposed bychemical or physical means.

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Elements

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Reconsidering the Fire ElementThe phlogiston theory viewed phlogiston as a

component of all matter.

The burning of a material was considered to be the

escaping of phlogiston from the matter.

If a material did not burn, it was considered to contain no

phlogiston.

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The phlogiston theory.

(A) In this theory,

burning was considered

to be the escape of

phlogiston into the air.

(B) Smelting combined

phlogiston-poor ore withphlogiston from a fire to

make a metal. (C) Metal

rusting was considered tobe the slow escape of

phlogiston from a metal

into the air.

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Discovery of Modern ElementsAntoine Lavoisier suggested that burning was actually a

chemical combination with oxygen.

Lavoisier realized that there needed to be a new conceptof elements, compounds, and chemical change.

We now know that there are 89 naturally-occurring

elements and at least 23 short-lived and artificially

prepared.

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Priestley produced a gas (oxygen) by using sunlight to heat

mercuric oxide kept in a closed container. The oxygen

forced some of the mercury out of the jar as it was

produced, increasing the volume about five times.

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Lavoisier heated a measured amount of mercury to

form the red oxide of mercury. He measured theamount of oxygen removed from the jar and theamount of red oxide formed. When the reaction wasreversed, he found the original amounts of mercury

and oxygen.

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The number of known elements increased as new

chemical and analytical techniques were developed.

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Names of Elements

The first 103 elements have internationally acceptednames, which are derived from:

The compound or substance in which the element was

discovered

An unusual or identifying property of the element

Places, cities, and countries

Famous scientists

Greek mythology Astronomical objects.

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Here are some of the symbols Dalton used for atomsof elements and molecules of compounds. Heprobably used a circle for each because, like theancient Greeks, he thought of atoms as tiny, round

hard spheres.

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Chemical Symbols

There are about a dozen common elements that have s

single capitalized letter for their symbol

The rest, that have permanent names have two letters.

the first is capitalized and the second is lower case.

Some elements have symbols from their Latin names.

Ten of the elements have symbols from their Latin or

German names.

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Symbols and Atomic Structure

A molecule is a particle that is composed of two or

more atoms held together by a chemical bond.

Isotopes are atoms of an element with identical

chemical properties, but different masses due to a

difference in the number of neutrons. The atomic mass of an element is the average of all

the atomic masses of the isotopes.

an isotopes contribution is determined by its

relative abundance.

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Using information from the fixed mass ratios of

combining elements, Dalton was able to calculate

the relative atomic masses of some of the elements.

Many of his findings were wrong, as you can see

from this sample of his table.

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The mass of an element is the mass of the element

compared to an isotope of carbon Carbon 12.

Carbon 12 is assigned an atomic mass of 12.00 g.

12.00 is one atomic mass unit

The number of protons and neutrons in an atom is its

mass number.

Atomic numbers are whole numbers

Mass numbers are whole numbers

The atomic mass is not a whole number.

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A schematic of a mass spectrometer. The atoms of a sample

of gas become positive ions after being bombarded by a

beam of electrons. The ions are deflected into a curved pathby a magnetic field, which separates them according to their

charged-to-mass ratio. Less massive ions are deflected the

most, so the device identifies different groups of particles

with different masses.

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A mass spectrum of chlorine from a massspectrometer. Note that that two separate masses ofchlorine atoms are present, and their abundance canbe measured from the signal intensity. The greater

the signal intensity, the more abundant the isotope.

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The Periodic Law

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Dmitri Medeleev gave us a functional scheme with

which to classify elements. Mendeleevs scheme was based on chemical properties

of the elements.

It was noticed that the chemical properties of elements

increased in a periodic manner.

The periodicity of the elements was demonstrated by

Medeleev when he used the table to predict to occurrence

and chemical properties of elements which had not yetbeen discovered.

Mendeleev left blank

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Mendeleev left blankspaces in his table whenthe properties of theelements above and

below did not seem tomatch. The existence ofunknown elements was

predicted by Mendeleev

on the basis of the blankspaces. When theunknown elements werediscovered, it was found

that Mendeleev hadclosely predicted the

properties of the elementsas well as their discovery.

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The Periodic Law

Similar physical and chemical properties recur

periodically when the elements are listed in order ofincreasing atomic number.

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The Modern Periodic Table

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Introduction

The periodic table is made up of rows of elements and

columns.

An element is identified by its chemical symbol.

The number above the symbol is the atomic number

The number below the symbol is the rounded atomic

weight of the element.

A row is called a period

A column is called a family

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(A) Periods of the periodic table, and (B) families of

the periodic table.

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Periodic Patterns

The chemical behavior of elements is determined by its

electron configuration

Energy levels are quantized so roughly correspond to

layers of electrons around the nucleus.

A shell is all the electrons with the same value of n. n is a row in the periodic table.

Each period begins with a new outer electron shell

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Each period ends with a completely filled outer shell that

has the maximum number of electrons for that shell.

The number identifying the A families identifies the

number of electrons in the outer shell, except helium

The outer shell electrons are responsible for chemical

reactions.Group A elements are called representative elements

Group B elements are called transition elements.

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Chemical Families

IA are called alkali metals because the react with water

to from an alkaline solution

Group IIA are called the alkali earth metals because

they are reactive, but not as reactive as Group IA.

They are also soft metals like Earth.

Group VIIA are the halogens

These need only one electron to fill their outer shell

They are very reactive.

Group VIIIA are the noble gases as they have

completely filled outer shells

They are almost non reactive.

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Four chemical families of the

periodic table: the alkali metals

(IA), the alkaline earth metals

(IIA), halogens (VII), and thenoble gases (VIIIA).

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Metals, Nonmetals, and Semiconductors

Chemical behavior is determined by the outer electrons. These are called valence electrons

These outer shell electrons are represented using electron

dot diagrams.

The noble gases have completely filled outer shells and

are therefore stable.

All other elements react so as to fill their outer shell and

become more stable.

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Electron dot notation for the representative

elements.

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When an atom or molecule gain or loses an electron it

becomes an ion. A cation has lost an electron and therefore has a

positive charge

An anion has gained an electron and therefore has anegative charge.

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Elements with 1, 2, or 3 electrons in their outer shell tend

to lose electrons to fill their outer shell and become

cations. These are the metals which always tend to lose electrons.

Elements with 5 to 7 electrons in their outer shell tend to

gain electrons to fill their outer shell and become anions. These are the nonmetals which always tend to gain electrons.

Semiconductors (metalloids) occur at the dividing line

between metals and nonmetals.

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The location of metals, nonmetals, and

semiconductors in the periodic table.

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(A) Metals lose their outer electrons to acquire a

noble gas structure and become positive ions. (B)

Nonmetals gain electrons to acquire an outer noble

gas structure and become negative ions.

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