Atoms

What are atoms? An atom is the smallest piece of an element. It is one million times smaller than the width of a piece of hair. Each type of atom represents a different element on the Periodic Table. All matter is made of atoms.

What are the sections of an atom. What are the parts of an atom What are the sections of an atom? What are the parts of an atom? Where can each part be found? An atom has a nucleus in the center surrounded by the electron cloud. An atom has three parts: protons, neutrons and electrons. Protons and neutrons are found in the nucleus. Electrons whiz around outside of the nucleus in the electron cloud.

Atoms Each atom is different because of the number of protons it has. This is called the atomic number. Atoms are arranged on the Periodic Table by their atomic number, or, by the number of protons in the nucleus.

Na Cl 11 17 Find the atomic numbers for Sodium (Na) and for Chlorine (Cl). Na Cl 11 17 What do these numbers represent? The number of protons!

Soft, silver metal that explodes when in contact with water!

Cl, #17 Pale green, poisonous gas used in chemical warfare during WW1.

Does an atom have mass? Atoms are so small that their mass is measured in atomic mass units, amu. Each proton is 1 amu. Each neutron is 1 amu. An electron is 0 amu. Where is most of the mass of an atom? 0 amu 1 amu 1 amu

Atomic Mass Na 22.989768 amu Cl 35.4527 amu Do you notice an issue here?

Atomic Mass The mass of an atom is in its nucleus. The mass is equal to the number of protons and neutrons. Protons + Neutrons = Atomic Mass

Atomic Mass The number of neutrons in an atom is not given on the Periodic Table. To determine the number of neutrons you round the atomic mass and subtract the atomic number.

Atomic Mass rounded atomic mass – atomic number = number of neutrons (protons + neutrons) – protons = neutrons

Atomic Mass Examples Sodium, Na, is atomic #11 and has a mass of 22.98 amu 23 – 11 = 12 neutrons Chlorine, Cl, is atomic #17 and has a mass of 35.45 amu 35 – 17 = 18 neutrons

Na has 11 protons and 12 neutrons. What is its atomic mass? Cl has 17 protons and 18 neutrons. What is its atomic mass? 23 amu 35 amu

Isotopes An isotope is an atom of an element that has a different number of neutrons than the “normal” atom of that element. every element has at least 2 isotopes since each isotope has a different number of neutrons, each has a different atomic mass the masses of all of the isotopes are averaged and the result is printed on the Periodic Table

Isotopes Protons Neutrons Atomic Mass Normal Hydrogen 1 0 1 Deuterium 1 1 2 Tritium 1 2 3 Water made with these isotopes of hydrogen is heavier than normal water. It is called “heavy water.”

Does an atom have charges? Protons are positive (+) Neutrons are neutral (0) Electrons are negative (-) Is the nucleus charged? Is the electron cloud charged? - +

Does an atom have charges? Protons are positive (+) Neutrons are neutral (0) Electrons are negative (-) The nucleus is positive. The electron cloud is negative. Because an atom has the same number of + protons and - electrons, an atom is neutral. - +

A neutron walks into a coffee shop and orders a latte A neutron walks into a coffee shop and orders a latte. He takes out his wallet to pay for it but the clerk behind the counter says: “Oh, no charge for you!”

Electron Clouds The electron cloud is the area surrounding the nucleus. The electrons whiz around here. Most of the area is empty space! Electrons are arranged into energy levels called shells or orbitals. When the shell is full, it is said to be complete.

Electron Configuration Electrons fit into the shells around a nucleus in an arrangement called the electron configuration. Electrons farther from the nucleus have more energy.

Electron Configuration Example: Sodium (Na) has an electron configuration of 2-8-1. 2 electrons in K shell 8 electrons in L shell 1 electron in M shell

Electron Configuration Example: Chlorine (Cl) has an electron configuration of 2-8-7. 2 electrons in K shell 8 electrons in L shell 7 electrons in M shell

Electron Configuration When you add the numbers in the electron configuration, you get the atomic number! K shell – closest to nucleus, holds 2 electrons L shell – holds up to 8 electrons M shell – holds up to 8 or up to18 electrons N shell – holds up to 18 or up to 32 electrons There are also O, P and Q shells for a maximum of 7 energy levels.

Are the shells “complete”? Sodium: 2 electrons in K shell full 8 electrons in L shell 1 electron in M shell not full Since this last shell is not full, the atom is not complete!

Are the shells “complete”? Chlorine 2 electrons in K shell full 8 electrons in L shell 7 electrons in M shell not full Since this last shell is not full, this atom Is not complete!

Valence Electrons Electrons in the shell farthest from the nucleus are called valence electrons. These electrons form chemical bonds with other atoms and give elements their chemical properties. Atoms combine with other atoms to complete their outermost or last energy level, called the valence shell.

How many valence electrons do you have? Na has 1 Cl has 7

Na has 1 valence electron. Cl has 7 valence electrons. Write Na on your board. Write Cl on your board. Draw one dot to the right of Draw two dots to the left, the symbol. two dots on top, two dots on the bottom, and one dot to the right of the symbol. Lewis Dot Structures

Chlorine, what do you want more than anything in the whole wide world?

Sodium, you are in danger! Why?

More on Atoms Because atoms have the same number of positive protons and negative electrons, atoms are neutral. They have no charge. If an atom loses or gains electrons, it is called an ion. An ion is a charged particle.

Ions If an atom loses an electron (-), would it be a positive or negative ion?

Ions If an atom loses an electron (-), would it be a positive or negative ion? Positive because you are taking away a negative charge so there are more protons than electrons Example: Sodium has 11 protons and 11 electrons. If it loses an electron, it has 11 positive protons but only 10 negative electrons.

Ions If an atom gains an electron (-), would it be a positive or negative ion?

Ions If an atom gains an electron (-), would it be a positive or negative ion? Negative because you are adding a negative charge so there are more electrons than protons Example: Chlorine has 17 protons and 17 electrons. With an additional electron, chlorine has 17 positive protons and 18 negative electrons.

Chlorine, add an electron to your Lewis Dot Structure. What type of ion are you? Draw that sign on your board. Sodium, erase your electron from your Lewis Dot Structure.

What happens to opposites?

When atoms bond, they create a new substance. Na + Cl → ?