2. Atomic Structure and the Periodic Table

3. 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

4. Structure of the Nuclear Atom
Thomson’s experiment- showed that atoms contained electrons

5. Thomson’s Cathode Ray Tube

7. Plum Pudding Model

8. 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

9. Atomic Structure 9

10. Structure of the Nuclear Atom
Rutherford’s Experiment- showed that atoms have a dense nucleus

11. Rutherford’s Model

12. Atomic Structure Nucleus –
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 12

13. Subatomic Particles Subatomic Particle Location Charge Mass Proton
Nucleus +
Yes
Neutron
Electron
Electron Cloud – No 13

14. Bohr Model of the Atom
Determined that electrons orbit the nucleus in specific energy levels
Electron Level 1 2 3 4
Electrons in Level 8 18 32

15. Bohr Model

16. 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. 16

17. The # of protons = atomic number
Identify the element…
Let's Count - 2 3 4 1 7 6 5
NITROGEN!
7 protons, so… 17

18. Distinguishing Between Atoms
Practice- How many protons and electrons are in each atom?
Fluorine
Aluminum
calcium

19. Mass number = # of protons + # of neutrons
Find the mass number…
Let's Count - 2 9 8 4 3 10 14 12 11 13 1 6 5 7 14
So the mass number is… 19

20. Distinguishing Between Atoms
Practice- How many protons, electrons and neutrons are in the following atoms?
Atomic Number Mass Number
Beryllium
Neon
Sodium

21. Mass number – atomic number = neutrons
Practice- How many neutrons are in each atom?
168 O
10847 Ag
20782 Pb

22. Practice Questions:
Use the information below to answer the questions that follow.
What is the name of this element?
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 22

23. Distinguishing Between Atoms
What is the difference?
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!!!

24. The picture shows a model of the element –
Fluorine
Carbon
Beryllium
Oxygen 24

25. Label each part of the diagram above. W – Nucleus X – Neutron
Y – Proton
Z – Electron 25

26. 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

27. 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?

28. 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 amu (50.69%) and (49.31%)

29. Practice 2- Element X has two natural isotopes
Practice 2- Element X has two natural isotopes. The isotope with a mass of has a relative abundance of 19.91%. The isotope with a mass of 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 and the exact masses of the isotopes are amu and amu.

30. The Periodic
Table of
Elements 30

31. The Periodic Table
Mendeleev- arranged the elements by increasing atomic mass

32. The Modern Periodic Table- shows all the known elements in order of increasing atomic number

33. What do these have in common?
Group –elements located in the same column.
What do these have in common?
Some Examples
Period – elements in the same row. 33

34. The periodic table is organized to group elements with similar properties in vertical columns

35. Group A - Representative Elements Group B - Transition Metals35

36. gain electrons to become negative ions dull brittle
NONMETALS
Iodine
Sulfur
gain electrons to become negative ions
dull
brittle
poor conductors of heat and electricity
usually gases at room temperature 36

37. lose electrons to become positive ions shiny malleable ductile
METALS
lose electrons to become positive ions
shiny
malleable
ductile
good conductors of heat and electricity
usually solids at room temperature 37

38. NONMETALS METALLOIDS METALS Right of the staircase
Left of the staircase
On the staircase 38

39. 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 table
Metalloids- 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

40. Natural States of the Elements Diatomic Elements

41. BrINClHOF Elements- diatomic

42. 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

43. Practice Questions:
Which of the following groups contains members with similar chemical activity?
Li, Be, C
Be, Mg, Sr
Sc, Y, Zr
C, N, O 43

44. Which of the following elements is. rarely involved in bonding because
Which of the following elements is rarely involved in bonding because it is already stable? Ca O Ar Cl 44

45. Elements in Group 16 of the periodic table usually –
form large molecules
gain electrons when bonding
act like metals
solidify at room temperature 45

46. A new element is discovered
A new element is discovered. It can be hammered flat into sheets and made into wire. The element is most likely –
a metal
hydrogen
a nonmetal
a metalloid 46