Atomic Atomic

StructureStructure

Elements and Atoms• Element- a pure substance made up of

only one type of atom.

•Atom- smallest unit of an element that maintains the properties of

that element.

Types of Elements

1. Metals- good conductor, lustrous, malleable, ductile. Left of zigzag line.

2. Nonmetals- poor conductor, most are gases at room temperature. Right of zigzag line.

3. Metalloids- characteristics of metals and nonmetals. On the zigzag line.

Inside the Atom

Protons: 1) positively charged particles 2) define the element 3) equal to the atomic number

Neutrons: 1) neutrally charged particles2) approximately the same

size as protons (a bit more)

Electrons: 1) negatively charged particles2) A lot smaller than the

protons or neutrons

On the Periodic Table On the Periodic Table you see…you see…

Atomic Number Atomic Symbol

Avg. Atomic Mass

Element

Understanding the Periodic Understanding the Periodic TableTable

Atomic Number:Atomic Number: the unique number of an the unique number of an element defined by the number of protonselement defined by the number of protonsEquals the number of electrons Equals the number of electrons

Atomic Symbol:Atomic Symbol: an abbreviation of an an abbreviation of an elementelement

Average AtomicAverage Atomic MassMass: the average of : the average of mass numbers of the isotopes of an mass numbers of the isotopes of an elementelement

Isotopes • atoms of the same element with

different masses (mass numbers)• same number of protons• different number of neutrons

Mass Number• mass of protons + mass of neutrons•This number can vary between atoms This number can vary between atoms of an element.of an element.

Three Isotopes of Hydrogen:Three Isotopes of Hydrogen:

Protium (99.9885%), Deuterium (0.0115%), Protium (99.9885%), Deuterium (0.0115%), TritiumTritium

Average atomic mass: 1.0079 Average atomic mass: 1.0079

QuestionQuestion

All isotopes of hydrogen containAll isotopes of hydrogen contain

a. one neutrona. one neutron c. one protonc. one proton

b. two electronsb. two electrons d. two nucleid. two nuclei

Sample

Mass Spectrometer

Electron Field Accelerator

Charged Particle Beam

Magnet

Heaviest Particles

Lightest Particles

Detector

According to a mass spectrometer experiment, the following data is obtained using a Nitrogen sample:

99.64% atoms are N 14 isotopes 0.36% atoms are N 15 isotopes

What is the weighted average?

Two ways to represent Isotopes of an atom:1) Hyphen Notation:

- element name – mass # Ex: hydrogen - 3

2) Nuclear symbol

mass = upper left hand number# protons = lower left hand number

Deuterium = 21H

Tritium = 31H

Given the nucleus below:

What is the mass number of this element? Which element is this?

The size of the nucleus:The size of the nucleus:

QuestionQuestion

Protons within a nucleus are Protons within a nucleus are attracted to each other byattracted to each other by

a. nuclear forcesa. nuclear forces

b. opposite chargesb. opposite charges

c. their energy levelsc. their energy levels

d. electron repulsiond. electron repulsion

QuestionQuestion

The nucleus of an atom has all The nucleus of an atom has all of the following characteristics of the following characteristics EXCEPT that itEXCEPT that it

a. is positively chargeda. is positively charged

b. is very denseb. is very dense

c. contains nearly all of the atom's massc. contains nearly all of the atom's mass

d. contains nearly all of the atom's volumed. contains nearly all of the atom's volume

The Charges:The Charges:

Proton: +1Proton: +1 mass = 1 amumass = 1 amuNeutron: 0 charge Neutron: 0 charge mass = 1amumass = 1amuElectron: -1Electron: -1 mass = .00055 amumass = .00055 amu

Atomic Mass Unit (amu)Atomic Mass Unit (amu)

1 atom chosen arbitrarily for the standard1 atom chosen arbitrarily for the standardcarbon-12 has a mass of 12 amucarbon-12 has a mass of 12 amu1amu = exactly 1/12 the mass of a 1amu = exactly 1/12 the mass of a

carbon-12 atomcarbon-12 atomThe atomic mass of any atom is The atomic mass of any atom is

determined by comparing it to carbondetermined by comparing it to carbon

How many protons, electrons & How many protons, electrons &

neutrons are in Carbon 14?neutrons are in Carbon 14?

Protons: Always 6 in carbonProtons: Always 6 in carbonElectrons: Same as protons, or 6Electrons: Same as protons, or 6Neutrons = Mass# - protonsNeutrons = Mass# - protonsNeutrons: 14 - 6 = 8 neutronsNeutrons: 14 - 6 = 8 neutrons

QuestionQuestion

An aluminum isotope consists of 13 An aluminum isotope consists of 13 protons, 13 electrons, and 14 protons, 13 electrons, and 14 neutrons. Its mass number isneutrons. Its mass number is

a. 13a. 13 c. 27c. 27

b. 14b. 14 d. 40d. 40

QuestionQuestion The atomic mass listed in the periodic The atomic mass listed in the periodic

table is the:table is the:

a. average atomic mass.a. average atomic mass.

b. relative atomic mass of the most b. relative atomic mass of the most

abundant isotope.abundant isotope.

c. relative atomic mass of the most c. relative atomic mass of the most

stable radioactive isotope.stable radioactive isotope.

d. mass number of the most abundant d. mass number of the most abundant

isotope.isotope.