1. Atoms, Elements, and Compounds

2. Why do we study Chemistry in Earth Science?
Chemistry is the study of matter.
Matter is anything that has mass and takes up space.
All living and non living things we study in Earth Science are made up of matter!

3. ATOMS Atoms are the building blocks of matter!
Atoms are very tiny but are made up of even smaller particles called neutrons, protons, and electrons.

4. Neutrons and Protons
Neutrons and protons are located in the center of an atom, called the nucleus.
Protons are positively charged particles.
Neutrons are particles that have no charge.

5. Electrons
Electrons are negatively charged particles located outside the nucleus.
Electrons are constantly moving around an atom’s nucleus in energy levels.
There are an equal number of protons and electrons in an atom, so the overall charge is zero

6. How do I tell how many protons, neutrons, and electrons are in an atom??

7. 1. Look at your Periodic Table of Elements.

8. The atomic number is the number of protons in an atom of an element.

9. Atoms must have equal numbers of protons and electrons…so, in our atom of krypton, we must have 36 electrons since it contains 36 protons.

10. 3. And the number of neutrons is…
The atomic weight is basically a measurement of the total number of particles in an atom’s nucleus.

11. To find the number of neutrons, you must first find the mass number.

12. Here, Krypton’s mass number is 84 since its atomic weight, 83
Here, Krypton’s mass number is 84 since its atomic weight, 83.80, rounds up to 84.

13. What do we find in an atom’s nucleus???
The mass number is a count of the number of particles in an atom’s nucleus.
What do we find in an atom’s nucleus???

14. PROTONS AND NEUTRONS!! So, 84= 36+?
Mass Number= (#of Protons)+ (# of Neutrons)
84= 36+?

15. The number of neutrons in an atom of krypton is

16. Summary… For any element, Number of Protons= Atomic Number
Number of Electrons= Number of Protons=Atomic Number
Number of Neutrons= Mass Number-Atomic Number

17. Electrons fill the energy levels outside the nucleus.
Level 1 holds 2 electrons.
Level 2 holds 8 electrons.
Level 3 holds 18 electrons.
Level 4 holds 32 electrons.
Level 5 holds 50 electrons.
Level 6 holds 72 electrons.
Energy levels do not have to be completely filled to start filling the next level.

18. Let’s try some on our own…
How many protons, neutrons, and electrons are found in each element?
Carbon (C)
Nitrogen (N)
Oxygen (O)
Phosphorus (P)
Calcium (Ca)
Hydrogen (H)

19. Atomic Radius size of atom
measured from center of nucleus to outside of electron cloud
expressed in picometers (1012 pm = 1 m)
usually pm

20. Example
An atom has a radius of 140 pm. How large is that in meters?

21. Now, what is an element???
An element is a pure substance that cannot be broken down into other substances by physical or chemical means.
Elements are made of only one type of atom.
There are 118 known elements, 94 occur naturally.

23. Isotopes
Although atoms of the same element have the same number of protons and electrons, atoms of an element can have different numbers of neutrons.
Atoms of the same element that have different numbers of neutrons are called isotopes.

24. Compounds
Elements can combine to form more complex substances. These substances are held together by chemical bonds (covalent and ionic.)
A compound is a pure substance formed when two or more different elements combine.

25. Compounds have several unique characteristics.
Compounds are always formed from a specific combination of elements in a fixed ratio. Ex: H2O
Compounds are chemically and physically different from the elements that form them.
Compounds cannot be broken down into simpler compounds by physical means, such as crushing or tearing.

26. Compounds can, however, be broken down by chemical means into simpler compounds or their original elements.
The End!