1. How are Atoms of the Same Element Different
Ions and Isotopes

2. How d0 particles in the atom stay together?
The four forces in an atom
How d0 particles in the atom stay together?
Four Forces

3. Why are all Atoms are Electrically Neutral?
If an atom gains or loses electrons the atom is no longer neutral .
Normally in an atom the number of electrons within the electron cloud is equal to the number of protons in the nucleus.
The positive and negative charges cancel each other out. Therefore, the atom is said to be electrically neutral.

4. Valence Electrons can move on or off atoms.
Electrons in the outer shells can move. All electrons in the outer shell are called VALENCE Electrons.
Valence Electrons can move on or off atoms.
Atoms can gain or lose electrons in the outer shell. Then they have a charge and are no longer neutral—the atom is now an ion.
This gaining or losing of electrons happens when atoms form molecules.

5. So an Atom can be changed
By adding or subtracting Electrons
+ Ions -
Ions

6. cation – ion with a positive charge
An ion is an atom, or group of atoms, that has a net positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation. Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl-
17 protons
18 electrons Cl
17 protons
17 electrons
2.5

7. Atoms want to have a stable octet or full outer shells.
Full shells = Stable Neutral Atoms
Atoms will gain or lose electrons to complete outer shells.

8. Gains an electron

9. Elements with 1, 2, or 3 electrons in their outer shell tend to lose electrons to fill their outer shell and become cations.
Elements with 5 to 7 electrons in their outer shell tend to gain electrons to fill their outer shell and become anions.

10. How to write Ions. Symbol + the number of electrons lost or gained.
+ sign if the atom became a cation
- sign if the atom became an anion
P= E= N=
P= E= N=
P= E= N=
P= E= N=

11. Atoms can also have different numbers of neutrons.
Changing its mass

12. How do we change the mass of an atom?
The mass of an atom is measured by the number of protons and neutrons. Protons and Neutrons have about the same mass=1amu

13. Changing an Atom’s mass doesn’t change its identity.
All atoms of an element have the same number of protons but the number of neutrons can vary. This change in neutron number forms an isotope.

14. Atoms with the same number of protons but differing numbers of neutrons are called ISOTOPES.
12 P and 12N =
12 P and 13N
with

15. Atomic Mass and Mass Number
Decimal No Decimals

16. Hydrogen and Hydrogen1

17. 2.3

18. Isotopes X Neon - 20 Magnesium - 22 Neon - 22
4.3 Q
- atoms of the same element with different # of n0 !!!
Three isotopes of Carbon:
Carbon - 12
(6p+, 6n0)
element of life
extremely rare
radioactive…carbon dating
Carbon - 13
(6p+, 7n0)
Carbon - 14
(6p+, 8n0)
-Compare to Atomic Mass Number:
Which of the following are isotopes of the same element?
Neon - 20
Neon - 22
Magnesium - 22 22 X 12 10 25
Same # of protons/atomic number

19. So Changing the number of Neutrons:
Changes the mass of the atom, but doesn’t change the atom’s properties.
Some Isotopes are unstable. The nucleus of unstable atoms do not hold together well.
Radioactive decay is the process whereby the nucleus of unstable isotopes release fast moving particles and energy. EX. Carbon dating

20. Atoms can be changed by
1. Creating Ions by adding or subtracting Valence Electrons 2. Creating Isotopes by changing the mass of the atom by altering the number of neutrons. Proton number does not change!!!!!!!!!