1. ATOMS AND ATOMIC STRUCTURE Atom Nucleus Proton Neutron Electron

2. WHAT IS AN ATOM? The smallest unit of an element.
Consists of a central nucleus surrounded by one or more electrons.

3. WHAT IS THE NUCLEUS? The central part of an atom.
Composed of protons and neutrons.
Contains most of an atom's mass.

4. WHAT IS A PROTON? Positively charged particle.
Found within an atomic nucleus.

5. WHAT IS A NEUTRON?
Uncharged particle.
Found within an atomic nucleus.

6. WHAT IS AN ELECTRON? Negatively charged particle.
Located in shells that surround an atom's nucleus.

7. Atomic Structure Atoms have 2 regions
1) Nucleus: the center of the atom that contains most of the mass of the atom.
2) Electron cloud: surrounds the nucleus & takes up most of the space of the atom.
Nucleus
Electron
Cloud

8. What is the Periodic Table?
I will be able to describe what an Element is and how to use the Periodic Table.
What is the Periodic Table?
Periodic Table
Chlorine
35.45 17 Cl
Element Name
Atomic #
Indicates the number of Protons.
Chemical Symbol
1-2 letter abbreviation
1st letter capitalized
2nd always lowercase
Atomic Mass
The weighted Average of the masses of the naturally occurring isotopes.

9. Mass # vs. Atomic Mass
Mass # ? = The Atomic mass on the periodic table rounded either up or down

10. How do we know the number of protons in an atom?
Atomic number (#)= # of protons in an atom
Ex: Hydrogen’s atomic # is 1
hydrogen has 1 proton
Ex: Carbon’s atomic # is 6
carbon has 6 protons
**The number of protons identifies the atom-it’s an atom’s fingerprint.

11. How do we know the number of neutrons in an atom?
Mass #: the # of protons plus neutrons in the nucleus
# of neutrons = mass # - atomic #
Example
Li has a mass # of 7 and an atomic # of 3
Protons = 3 (same as atomic #)
Neutrons= 7-3 = 4 (mass # - atomic #)

12. How do we find the number of electrons in an atom?
Most atoms are neutral (have no overall charge)
Because the only charged subatomic particles are the protons and electrons… they must balance each other out in an electrically neutral atom.
Therefore..
# Electrons = # Protons *
* (in a neutral atom..)

13. What is The Periodic Table?
I will be able to use the info displayed on the periodic table to determine characteristics of the elements.
What is The Periodic Table?
Chlorine
Periodic Table 17 Cl
Atomic #
Atomic Mass
(round this number)
35.45
# Protons = Atomic Number
# Neutrons = Atomic Mass - Atomic Number
# Electrons = Atomic Number

14. Examples He has a mass # of 4 and an atomic # of 2
p+ = 2 no = 2 e- = 2
Cl has a mass # of 35 and an atomic # of 17
p+ = 17, no = 18, e- = 17

15. Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons.

16. Hydrogen–1 (protium) 1 Hydrogen-2 (deuterium) Hydrogen-3 (tritium) 2
Isotope
Protons
Electrons
Neutrons
Nucleus
Hydrogen–1
(protium) 1
Hydrogen-2
(deuterium)
Hydrogen-3
(tritium) 2

17. We name the isotope based on its mass number
Naming Isotopes
We name the isotope based on its mass number
carbon-12
carbon-14
uranium-235

18. Isotopes
Elements occur in nature as mixtures of isotopes.

19. Atomic Mass How heavy is an atom of oxygen?
It depends.. b/c there are different oxygen isotopes.
We are more concerned with the average atomic mass.
This is determined based on the abundance of each isotope
We don’t use grams for this mass because the numbers would be too small.

20. Measuring Atomic Mass Instead we use the Atomic Mass Unit (amu)
defined as one-twelfth the mass of a carbon-12 atom.
Each isotope has its own atomic mass, thus we determine the average from percent abundance.

21. Composition of the nucleus
Atomic Mass
Atomic mass is the average of all the naturally occurring isotopes of that element.
Isotope
Symbol
Composition of the nucleus
% in nature
Carbon-12
12C
6 protons
6 neutrons
98.89%
Carbon-13
13C
7 neutrons
1.11%
Carbon-14
14C
8 neutrons
<0.01%
Carbon =

22. What are ions? An atom is neutral. Protons = Electrons
If an atom does not have the same
number of protons and electrons, an ion is formed. Protons do NOT equal electrons
When an atom loses or gains one or more electrons, it acquires a net electrical charge and it is called an ion.

23. EXAMPLE Number of protons = 12 - Number of electrons = 10 +2
A neutral magnesium (Mg) atom has 12 protons and
12 electrons. If the magnesium atom loses 2
electrons, it will have a net electrical charge of 2.
To find net charge of an ion, subtract the number of
electrons from the number of protons.
Number of protons = 12
Number of electrons =
A magnesium ion is represented as Mg+2.

24. EXAMPLE 1:
1. Sodium (Na) atoms have ____ protons and ____electrons with a net charge of ______.
  (+11 – 11 = 0)
2. If the Sodium ion has only 10 electrons, what is the net charge of the ion? ________.
( = +1)
3. What is the chemical symbol for this ion? ______________

25. EXAMPLE 2:
1. Beryllium (Be) atoms have ____ protons and ____electrons with a net charge of ____.
(+4 – 4 = 0)
2. If the Beryllium ion has only 2 electrons, what is the net charge of the ion? ______.
(+4 -2 = +2)
3. What is the chemical symbol for this ion? ______________

27. Nonmetals will gain electrons when forming compounds
Nonmetals will gain electrons when forming compounds. They become negatively charged because there will be more electrons than protons. A negative ion will be formed.
17P = +17
18E= -18
17P
18N
Cl ¯ 2 8 7
ionic charge: 1E= -1

28. Metals will lose electrons when forming compounds
Metals will lose electrons when forming compounds. They become positively charged because there will be more protons than electrons. A positive ion is formed.
11P
12N
Na⁺
2 8 1
11P = E = -10
ionic charge: 1P = +1

29. Metals will lose 1, 2, or 3 electrons in the last energy level to other elements. This will leave the last shell complete.
Nonmetals will gain 1, 2, or 3 electrons onto their outside
energy level from other
elements. This will
complete the last shell.

31. ATOMS ISOTOPES IONS Proton number, Atomic number
Never ever ever changes unless you change the element
Electron number = proton number
Because the atom is neutral
Neutron number, mass number – atomic number
ISOTOPES
Same proton number (as atom)
Same electron number (as atom)
Different neutron number
Different mass number
IONS
Different electron number
Same Neutron number (as atom)