Atomic Structure and the Periodic Table

Early Models of the Atom

Dalton’s Atomic Theory

- All elements are composed of atoms

- All atoms of a given element are identical

- Atoms of different elements are different

- Compounds consist of the atoms of different elements

- Atoms are not created or destroyed in a chemical change

Structure of the Nuclear Atom

Thomson’s experiment- showed that atoms contained electrons

Thomson’s Cathode Ray Tube

Plum Pudding Model

Structure of the Nuclear Atom

Electron- negatively charged subatomic particle

Proton- positively charged subatomic particle found in the nucleus of the atom

Neutron- a subatomic particle with no charge that is found in the nucleus

Atomic Structure

Structure of the Nuclear Atom

Rutherford’s Experiment- showed that atoms have a dense nucleus

Rutherford’s Model

Atomic StructureNucleus –• very dense (contains nearly all the mass of the atom yet occupies a very small space)

• location of positively charged protons and neutral neutrons

Electron Cloud – • space surrounding the nucleus• location of negatively charged electrons

Subatomic Particles

SubatomicParticle

Location Charge Mass

Proton Nucleus + Yes

Neutron Nucleus 0 Yes

Electron Electron Cloud – No

Bohr Model of the Atom

Determined that electrons orbit the nucleus in specific energy levels

Electron Level 1 2 3 4

Electrons in Level 2 8 18 32

Bohr Model

The # of protons = atomic number

• The number of protons determines the element. All atoms of the same element have the same # of protons.

• Count the protons and use the atomic number on the periodic table to identify the element.

The # of protons = atomic numberIdentify the element…

7 protons, so…

Distinguishing Between Atoms

Practice- How many protons and electrons are in each atom?

a. Fluorine

b. Aluminum

c. calcium

Find the mass number…

So the mass number is…

Mass number = # of protons + # of neutrons

Distinguishing Between Atoms

Practice- How many protons, electrons and neutrons are in the following atoms?

Atomic Number Mass Number

a. Beryllium 4 9

b. Neon 10 20

c. Sodium 11 23

Mass number – atomic number = neutrons

Practice- How many neutrons are in each atom?

a. 168 O

b. 10847 Ag

c. 20782 Pb

1. Use the information below to answer the questions that follow.

a. What is the name of this element?

b. What is the mass number of this element?

A certain element has a nucleus containing eight protons and ten neutrons and has ten electrons orbiting the nucleus.

Oxygen

18

Distinguishing Between Atoms

Isotopes- atoms with the same number of protons but different number of neutrons

Protons + Neutron = Atomic Mass

If the number of protons never changes than it’s the number of neutrons!!!

2. The picture shows a model of the element –

a. Fluorineb. Carbonc. Berylliumd. Oxygen

3. Label each part of the diagram above.W – NucleusX – NeutronY – ProtonZ – Electron

Distinguishing Between Atoms

Atomic mass- the weighted average of the masses of the isotopes of an element

- Atomic mass unit- a unit of mass equal to one-twelfth the mass of carbon twelve atom

Practice- The three isotopes of chromium are chromium-50, chromium-52, and chromium 53. How many neutrons are in each isotope, given that chromium always has an atomic number of 24?

Calculating average atomic mass

Average atomic mass = (fractional abundance of isotope 1)(mass of isotope 1) + (fractional abundance of isotope 2)(mass of isotope 2)

Practice 1. Calculate the atomic mass of bromine. The two isotopes of bromine have atomic masses and relative abundances of 78.92 amu (50.69%) and 80.92 (49.31%)

Practice 2- Element X has two natural isotopes. The isotope with a mass of 10.012 has a relative abundance of 19.91%. The isotope with a mass of 11.009 has a relative abundance of 80.09%. Calculate the atomic mass of this element.

Practice 3- Calculate the percent abundance of copper-63 if the atomic mass is 63.546 and the exact masses of the isotopes are 64.93 amu and 62.93 amu.

The Periodic Table

Mendeleev- arranged the elements by increasing atomic mass

The Modern Periodic Table- shows all the known elements in order of

increasing atomic number

Group –elements located in the same column.

Period – elements in the same row.

The periodic table is organized to group elements with similar

properties in vertical columns

• gain electrons to become negative ions• dull• brittle• poor conductors of heat and electricity• usually gases at room temperature

IodineSulfur

• lose electrons to become positive ions• shiny• malleable• ductile• good conductors of heat and electricity• usually solids at room temperature

Left of the staircaseRight of the staircaseOn the staircase

The Modern Periodic Table Metals- elements on the left side of the table - alkali metals- metals in group 1A - alkaline earth metals- metals in group 2A - transition and inner transition metals- group B, located in the

center of the tableMetalloids- have properties intermediate to metals and nonmetals

Nonmetals- elements on the right side of the table - halogens- nonmetals in group 7A - noble gases- elements in group 0

Natural States of the ElementsDiatomic Elements

BrINClHOF Elements- diatomic

The Modern Periodic Table

Periods- horizontal rows on the periodic table

Periodic law- when elements are arranged by increasing atomic number, there are periodic or repeating properties

Groups (families)- columns on the periodic table

- Group A elements- representative elements

- Group B elements- transition metals

1. Which of the following groups contains members with similar chemical activity?

a. Li, Be, Cb. Be, Mg, Src. Sc, Y, Zrd. C, N, O

3. Which of the following elements is rarely involved in bonding because it is already stable?

a. Cab. Oc. Ard. Cl

4. Elements in Group 16 of the periodic table usually –

a. form large moleculesb. gain electrons when bondingc. act like metalsd. solidify at room temperature

5. A new element is discovered. It can be hammered flat into sheets and made into wire. The element is most likely –

a. a metalb. hydrogenc. a nonmetald. a metalloid