1. The Atom

2. Crash Course

3. The Atom An atom consists of a nucleus
(made up of protons and neutrons)
electrons in space about the nucleus.
Electron cloud
Nucleus

4. Size of an Atom http://www.teachertube.com/video/power-of-ten-180460
A cube of sugar contains as many atoms as there are stars in the Universe!

5. The Atom consists of subatomic particles:
Proton (p+)
Located inside the nucleus
Positively charged particle
Neutron (n0)
Particle with no charge
Electron (e-)
Located in the orbitals surrounding nucleus
Negatively charged particle

6. Size of subatomic particles
Actual
mass (g)
Relative
mass
Name
Symbol
Charge
Electron e- -1
1/1840
9.11 x 10-28
Proton p+ +1 1
1.67 x 10-24
Neutron no 1
1.67 x 10-24
Protons & neutrons are about 1800X the size of electrons!!!!!!

7. The atom is mostly EMPTY SPACE
Field Trip!!!!!!!!!!!!!!
Therefore…
If the nucleus was the size of a marble, the electron would be the size of a grain of sand, and there would be 500 meters in between the nucleus and the electron.

9. Counting the Pieces Atomic Number = number of protons
# of protons determines kind of atom
Protons are the identification piece to the element!!! The number of protons in an atom
DO NOT CHANGE!!!!
Atomic Number = number of electrons in a neutral atom
Mass Number = the number of protons + neutrons
California WEB

10. Symbols
Contain the symbol of the element, the mass number and the atomic number X
Mass
number
Atomic
# protons
+ # neutrons
mass number
# protons

11. F Symbols 19 9 Find the number of protons number of neutrons
number of electrons
Atomic number
Mass number
= 9 + F 19 9
= 10
= 9
= 9
= 19

12. Br Symbols 80 35 Find the number of protons number of neutrons
number of electrons
Atomic number
Mass number
= 35
= 45 Br 80 35
= 35
= 35
= 80

13. Na Symbols 23 11 Find the number of protons number of neutrons = 11
number of electrons
Atomic number
Mass number
= 11 Na
= 12 23
=11 11
=11
=23
Sodium atom

14. Na Symbols 23 11 Find the 1+ number of protons number of neutrons
number of electrons
Atomic number
Mass number
= 11 Na
= 12 23 1+
= 10 11
= 11
= 23
Sodium ion

15. Symbols
If an element has an atomic number of 23 and a mass number of 51 what is the
number of protons
number of neutrons
number of electrons
Complete symbol
= 23
= 23
= 28
= 23 V 51 23

16. Symbols
If an element has 60 protons and 144 neutrons what is the
Atomic number
Mass number
number of electrons
Complete symbol
= 60
= 204 = Nd
204 60

17. IONS
IONS are atoms or groups of atoms with a positive or negative charge.
Taking away an electron from an atom gives a CATION with a positive charge
Adding an electron to an atom gives an ANION with a negative charge.
To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2
Na Ca I O

18. Valence Electrons
Electrons in the outermost shell of an atom that can be lost or gained or be shared to make bonds
Representative Elements: can look at the group to determine the number of valence electrons

19. Forming Cations & Anions
A CATION forms when an atom loses one or more valence electrons.
An ANION forms when an atom gains one or more valence electrons
F + e- --> F-
Mg --> Mg e-

20. PREDICTING ION CHARGES
In general
metals (Mg) lose electrons ---> cations
nonmetals (F) gain electrons ---> anions

21. Learning Check – Counting
State the number of protons, neutrons, and electrons in each of these ions.
39 K O Ca +2
#p+ ______ ______ _______
#no ______ ______ _______
#e- ______ ______ _______

22. One Last Learning Check
Write the nuclear symbol form for the following atoms or ions:
A. 8 p+, 8 n, 8 e- ___________
B. 17p+, 20n, 17e- ___________
C. 47p+, 60 n, 46 e- ___________

23. Charges on Common Ions -3 -2 -1 +1 +2
By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.

24. Isotopes
Atoms of the same element (same Z) but different mass number (A).
Boron-10 (10B) has 5 p and 5 n
Boron-11 (11B) has 5 p and 6 n
10B
11B

25. Figure 3.10: Two isotopes of sodium.

26. Isotopes & Their Uses
Bone scans with radioactive technetium-99.

27. Isotopes & Their Uses
The tritium (isotope of H) content of ground water is used to discover the source of the water, for example, in municipal water or the source of the steam from a volcano. (Note: Tritium is illegal for public use in the U.S.)

28. Atomic Symbols sodium-23
Show the name of the element, a hyphen, and the mass number in hyphen notation
sodium-23
Show the mass number and atomic number in nuclear symbol form
mass number
23 Na
atomic number

29. Isotopes?
Which of the following represent isotopes of the same element? Which element?
234 X X 235 X 238 X

30. Learning Check – Counting
Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.
12C C 14C
#p+ _______ _______ _______
#no _______ _______ _______
#e- _______ _______ _______

31. Answers
12C C 14C #p
#no #e

32. 10B
11B
AVERAGE ATOMIC MASS
Because of the existence of isotopes, the mass of a collection of atoms has an average value.
Boron is 20% 10B and 80% 11B. That is, 11B is 80 percent abundant on earth.
For boron atomic weight
= (10 amu) (11 amu) = amu

33. Isotopes & Average Atomic Mass
Because of the existence of isotopes, the mass of a collection of atoms has an average value.
6Li = 7.5% abundant and 7Li = 92.5%
Avg. Atomic mass of Li = ______________
28Si = 92.23%, 29Si = 4.67%, 30Si = 3.10%
Avg. Atomic mass of Si = ______________