1. Atoms, Ions, and Molecules

2. Think about it…
What do a frog, a skyscraper, a car, and your body all have in common?

3. ATOMS!
Every physical thing you can think of, living or not, is made of incredibly small particles called atoms.

4. The atom The small basic unit of _____________. How small is an atom??
Matter – anything that takes
up space and has mass
How small is an atom??
Millions and millions of atoms could fit in the space the size of the period at the end of this sentence.

5. Atoms consist of three types of smaller particles:
Protons (+)
Neutrons (neutral)
Electrons (-)
Notice the location
of protons, neutrons,
and electrons in an atom

6. Element
Element – type of atom that can’t be broken down into a simpler substance
Examples of elements:
Hydrogen
Lithium
Carbon
Boron

7. How do we identify an element?
Answer = by the number of protons
Think about it: if Krypton loses a proton, is it still Krypton??
Atomic Number = number of protons

8. How can we identify the number of:
Protons = ____________
Neutrons = ___________
Electrons = ___________
From this picture?

9. THEN complete the formula below:
Atomic Number = number of protons
**Number of protons and electrons is the same
Atomic Weight
To find the number of neutrons you have to find the mass number. To find the mass number, all you need to do is round the atomic weight to the nearest whole number. In our example, krypton's mass number is 84 since its atomic weight, 83.80, rounds up to 84.
THEN complete the formula below:
Mass Number = (Number of Protons) + (Number of Neutrons)
84 = (36) (??)

10. Elements
What four elements make up 96% of a human’s body mass?? 1.) 2.) 3.) 4.)

11. Elements
What four elements make up 96% of a human’s body mass?? 1.) Carbon 2.) Oxygen 3.) Nitrogen 4.) Hydrogen

12. Review Where are protons and neutrons found in the atom?
Where are the electrons found in the atom?

13. The Bohr Model Niels Bohr introduced “The Bohr Model” in 1913
Model that shows the atoms electrons located outside the nucleus in regions called energy levels (valence shell)
Energy levels

14. The Bohr Model The first energy level can ONLY have up to 2 electrons
The remaining energy levels can have up to 8
Energy level

15. Practice
Draw a Bohr model of an oxygen and calcium carbon atom.

16. Figure 2.3 Electron configurations-overview

17. Isotope – same number of protons (same element) different number of neutrons (different mass) Example: Carbon 12, Carbon 13, Carbon 14

18. Figure 2.2 Nuclei of the three naturally occurring isotopes of carbon-overview

19. When atoms gain or lose electrons
Ions – an atom that gained or lost one or more electrons is called an ion
Why do atoms gain or lose electrons?
Atoms want a full outermost energy level (valence shell)
When an atom loses or gains electrons it has an electrical charge (positive or negative)

20. For example:
Sodium (Na) has how many electrons?
Chlorine (Cl) has how many electrons?
Draw the Bohr model for each
Who is closer to having a full outermost electron shell??

21. Na will give one of its electrons to chlorine
Becomes Na+ = positive charge = cation
Cl will gain an electron from Na
Becomes Cl- = negative charge = anion

22. Why are Ions important?
Hydrogen ions (H+) are needed for the production of usable chemical energy in cells
Calcium ions (Ca2+) are necessary for every muscle movement in your body
Chloride ions (Cl-) are important for sending chemical signals to your brain

23. Ionic Bonds
Forms through the electrical force between oppositely charged ions
Think back to NaCl that we just talked about

24. Ionic Bond Have you ever heard positive and negative attract?
It’s the same here!
Na+ attracts to Cl-
NaCl = table salt
The positive sodium ion (Na+) and negative chloride ion (Cl-) attract to each other and form an ionic bond

25. BUT, Not all atoms easily gain or lose electrons…
It is possible for atoms to share electrons
A covalent bond forms when atoms share a pair of electrons
Draw a Bohr model for oxygen and carbon
How many electrons does oxygen need to fill its outermost shell?
How many electrons does carbon need to fill its outermost shell?

26. Carbon dioxide (CO2) is a covalent bond
An oxygen atom needs two electrons to fill its outer energy level. A carbon atom needs 4 electrons to fill its outer energy level. In carbon dioxide, carbon makes a double bond, or SHARES two pairs of electrons with each oxygen atom

27. Water (H2O) is a covalent bond

28. What is a molecule?
Molecule- two or more atoms held together by covalent bonds
For example: H2O, CO2, O2, etc.
**Almost all of the substances that make up organisms are molecules held together by covalent bonds

29. Compounds
A substance made of different elements bonded together in a certain ratio
Held together by chemical bonds
H2O, CO2, NaCl….can you think of any others?