Chapter 4: The atomChapter 4: The atom

P 93 – 101 and 109-112P 93 – 101 and 109-112

What is an atom?What is an atom?

Atoms:Atoms: Makes up all matterMakes up all matter Are incredibly smallAre incredibly small Determines the properties of matterDetermines the properties of matter 91 different types of atoms91 different types of atoms 20 synthetic atoms20 synthetic atoms

The atomic theoryThe atomic theory

John Dalton devised a theory of the atom John Dalton devised a theory of the atom in 1808in 1808 Each element is composed of tiny Each element is composed of tiny

indestructible particles called atomsindestructible particles called atoms All atoms of a given element have the same All atoms of a given element have the same

mass and properties that distinguishes them mass and properties that distinguishes them from other atoms/elementsfrom other atoms/elements

Atoms combine in simple, whole number Atoms combine in simple, whole number ratios to form compoundsratios to form compounds

History of the atomHistory of the atom

J.J Thompson (1856 J.J Thompson (1856 – 1940)– 1940) Discovered the Discovered the

electronelectron• Negative chargeNegative charge• Smaller and lighterSmaller and lighter• Assumed to be a Assumed to be a

positive charge within positive charge within the atom to balance the atom to balance electrons: plum electrons: plum pudding modelpudding model

History of the atomHistory of the atom Ernest Rutherford (1909)Ernest Rutherford (1909)

Gold foil experimentGold foil experiment Alpha particles (+ charge) Alpha particles (+ charge)

toward gold foil.toward gold foil. Alpha particles where Alpha particles where

deflected….there must be deflected….there must be a large concentration of + a large concentration of + chargecharge

Came up with nuclear Came up with nuclear theory of the atomtheory of the atom

History of the atomHistory of the atom Nuclear theory of the Nuclear theory of the

atomatom Most of the atoms mass Most of the atoms mass

and positive charge is in and positive charge is in the nucleusthe nucleus

Most of the volume of Most of the volume of the atom is empty space the atom is empty space where tiny electrons sitwhere tiny electrons sit

There are as many + There are as many + charges as – charges so charges as – charges so the atom is neutralthe atom is neutral

Conclusions:Conclusions: The nucleus contains The nucleus contains

Protons (+) and Protons (+) and neutrons (neutral)neutrons (neutral)

The nucleus makes up The nucleus makes up 99.9% of the mass of 99.9% of the mass of the atomthe atom

The electrons are The electrons are present in a cloud present in a cloud surrounding the surrounding the nucleusnucleus

Atomic mass/atomic numberAtomic mass/atomic number

What are the 3 subatomic particles?What are the 3 subatomic particles? Which of the subatomic particles identifies Which of the subatomic particles identifies

an element? an element? PROTONS! Each element has a different PROTONS! Each element has a different

number of protons, thus making it unique.number of protons, thus making it unique. Atomic Number: the # of protons in the Atomic Number: the # of protons in the

nucleus of an atomnucleus of an atom The # of protons is equal to the # of The # of protons is equal to the # of

electrons.electrons. Why?Why?

Atomic Number

Problems:Problems:

How many protons are in Al?How many protons are in Al? 1313

How many protons are in V? How many protons are in V? 2323

How many electrons are in Copper?How many electrons are in Copper? 2929

Mass NumberMass Number

In an atom, where In an atom, where is most of the mass is most of the mass located?located? In the nucleus In the nucleus

What subatomic What subatomic particles are in the particles are in the nucleus? nucleus? Protons & Protons &

NeutronsNeutrons

Mass number is Mass number is the mass found in the mass found in the nucleusthe nucleus mass number: # mass number: #

of protons + # of of protons + # of neutronsneutrons

You can find mass You can find mass number by looking number by looking at the shorthand at the shorthand notation. notation.

Shorthand NotationShorthand Notation Used to show the mass # and atomic number of Used to show the mass # and atomic number of

an element.an element.

14 is the mass #14 is the mass # 7 is the atomic #7 is the atomic # N is the symbol for nitrogenN is the symbol for nitrogen

N147

Shorthand NotationShorthand Notation

Can also be written as: element-mass #Can also be written as: element-mass # Examples Nitrogen-14, Nitrogen-15, Nitrogen-Examples Nitrogen-14, Nitrogen-15, Nitrogen-

1616 How many neutrons are in each of the How many neutrons are in each of the

above elements? above elements? What is the shorthand notation for What is the shorthand notation for

gold-197?gold-197?

Try TheseTry These

What is the mass number of What is the mass number of 4040Ca?Ca? 4040

How many neutrons are in germanium-73?How many neutrons are in germanium-73? 41 41

How many protons, electrons & neutrons How many protons, electrons & neutrons does zinc-65 have? does zinc-65 have? Protons: 30Protons: 30 Electrons: 30Electrons: 30 Neutrons: 35Neutrons: 35

IsotopesIsotopes

Think about pizza…..Think about pizza….. Isotopes are similar forms of the same Isotopes are similar forms of the same

element.element. More specifically, isotopes have the same More specifically, isotopes have the same

number of number of protonsprotons, but different number , but different number of of neutronsneutrons..

If neutrons change, what else changes? If neutrons change, what else changes? MassMass

Atomic MassAtomic Mass

We must take in account all of the We must take in account all of the isotopes in order to get an accurate mass.isotopes in order to get an accurate mass.

The mass on the PT is a weighted The mass on the PT is a weighted average of all the naturally occurring average of all the naturally occurring isotopes of an element.isotopes of an element.

This is called atomic mass. This is called atomic mass.

Carbon IsotopesCarbon Isotopes

Carbon has several isotopesCarbon has several isotopes The two most naturally occurring isotopes The two most naturally occurring isotopes

are carbon-12 and carbon-13 are carbon-12 and carbon-13 This means C-12 and C-13 account for all This means C-12 and C-13 account for all

of the atomic mass. of the atomic mass. So how do we calculate atomic mass? So how do we calculate atomic mass?

Carbon IsotopesCarbon Isotopes

Carbon-12Carbon-12 Mass: 12.000 amuMass: 12.000 amu

(amu: atomic mass (amu: atomic mass unit)unit)

Abundance: 98.89%Abundance: 98.89%

How many neutrons How many neutrons are in carbon-12?are in carbon-12?

Carbon-13Carbon-13 Mass: 13.003 amuMass: 13.003 amu Abundance: 1.11%Abundance: 1.11%

How many neutrons How many neutrons are in carbon-13?are in carbon-13?

Carbon IsotopesCarbon Isotopes

Atomic mass=(mass of isotope 1 x abundance) Atomic mass=(mass of isotope 1 x abundance) + (mass of isotope 2 x abundance) + (mass of + (mass of isotope 2 x abundance) + (mass of isotope 3 x abundance) isotope 3 x abundance)

(12.000 x .9889) + (13.001 x .0111)=12.011 (12.000 x .9889) + (13.001 x .0111)=12.011 amuamu

Find this value on your PT!Find this value on your PT!

Hydrogen IsotopesHydrogen Isotopes

Hydrogen-1Hydrogen-1 Name: protiumName: protium

Hydrogen-2Hydrogen-2 Name: deuterium Name: deuterium

1e

1 p0 n

1e

1 p1 n

Hydrogen IsotopesHydrogen Isotopes

Hydrogen-3Hydrogen-3 Name: tritium Name: tritium

1e

1 p2 n