Structure of an Atom

1. Structure of an Atom When you read the Periodic Table, one of the most common questions is, “Why do the names not match the symbol?” The reason is that the names do match the symbol, but it is the Latin name.

2. Example: • Silver – • Symbol – Ag • Latin Name: Argentum

3. Atomic Components • An element is matter that is composed of one type of atom, which is the smallest piece of matter that still retains the property of the element.

4. The parts: • Atoms are composed of particles called: • Protons (+) • Neutrons (no charge) • Electrons (-)

5. The Mass: • Protons and Neutrons are found in a small, positively charged (+) center of the atom called the nucleus that is surrounded by a cloud containing electrons. • (If both protons and neutrons are found in the nucleus, why is it positive (+)?)

6. Diagram • Protons = positively charge 1+ • Neutrons = do not have a charge (o) • Electrons = negatively charge 1- • Atoms of different elements differ in the number of protons they contain.

7. New Material - Quarks • Even Smaller – • Protons and Neutrons are made up of smaller particles called quarks. Scientists have confirmed the existence of six uniquely different quarks. Scientists theorize that the arrangement of three quarks held together with the strong nuclear force produces a proton. 3 more makes a neutron.

8. Quarks -

9. Quarks • To find quarks, scientists accelerate charged particles to tremendous speeds then force them to collide with other protons.

10. Models • Scientists use models to represent things that are difficult to visualize, (that means see in your mind)

11. Atoms • Atoms are very small. It would take about 24,400 atoms staked on top of each other to equal the thinness of a sheet of aluminum foil. • To study them, scientists developed models that they can use to visualize how the atom is constructed

12. The Model has changed. • Democritus proposed the idea that atoms make up all substance in… • 400 B.C. • But Aristotle disputed Democritus’ Theory saying that all matter is uniform throughout and not composed of smaller particles.

13. Aristotle’s Theory • Aristotle’s Idea was accepted for over 2000 years. • See what happens when you don’t study before you say things. They tend to be WRONG!! • Anyhow, he didn’t have the technology that we have today either.

14. John Dalton • In the 1800’s John Dalton provided a model of the atom as a solid sphere.

15. But over time and experiments, scientists have modified the atomic model. The model that we use today is the accumulated knowledge of almost 200 years.

16. Thompson’ s Model • The chocolate chip cookie model • What’s missing?

17. Rutherford’s Atom • What’s missing?

18. D Bohr Model • Diagram like planet’s orbitals.

19. Electron Cloud • Newest Model

20. Electron Cloud • Developed in 1926, the electron cloud is the area around the nucleus of an atom where its electrons are most likely found. • The electron cloud is 100,000 times larger than the diameter of the nucleus, but an electron is much smaller than a proton

21. The atom’s mass: • Proton = 2000 times larger than an electron. • Electrons = the electron cloud makes up an atom’s volume. (space) Electrons are very tiny.

22. Why we don’t see them. • Because an electron’s mass is small and the electron is moving so quickly around the nucleus, it is impossible to describe its exact location in the atom.

23. What do electrons do? • Each electron travels at an average distance form the nucleus, depending on its energy. • These average distances are referred to as energy levels. • Energy levels are areas of the cloud where the electrons are more likely to be found.

24. Energy Levels