6.1 Part 1: The Atom

anything that has mass and takes up space matter is made up of atoms What is Matter?

How Small are Atoms? A human hair is about 1 million carbon atoms wide A typical human cell contains roughly 1 trillion atoms A speck of dust might contain 3x1012 (3 trillion) atoms

What are Subatomic Particles? the smallest unit into which matter can be divided building blocks of all matter comprised of a nucleus (at it’s center) and an electron cloud (surrounding the nucleus) made up of sub-atomic particles smaller than an atom protons neutrons electrons What is an Atom? What are Subatomic Particles?

+ What are Protons? positively charged particles (+) help make up the nucleus of the atom equal to the atomic number of the atom contribute to the atomic mass equal to the number of electrons + - +

What are Neutrons? neutral particles; have no electric charge help make up the nucleus of the atom contribute to the atomic mass + -

- What are Electrons? negatively charged particles (-) found outside the nucleus of the atom in the electron orbits/levels each orbit/level can hold a maximum number of electrons 1st orbital = 2 electrons 2nd orbital = 8 electrons 3rd orbital = 8 electrons + - -

What are Electrons? mass is insignificant when compared to protons and neutrons equal to the number of protons involved in the formation of chemical bonds + - -

What are Valence Electrons? found in the outermost energy level of the electron cloud (called the valence shell) involved in bonding determine the chemical properties of an element

How is the Atom’s Center Formed? Protons and neutrons are grouped together to form the “center” or nucleus of an atom Notice that the electrons are not apart of the nucleus - + - - -

Atomic Structure

How are Atoms Described? atomic number = number of protons in a neutral atom, the # of protons = the # of electrons atomic mass= the number of protons + the number of neutrons

What would be the atomic number of this atom? the number of protons in the nucleus of an atom What is Atomic Number? - + - - What would be the atomic number of this atom?

+ What is the Atomic Mass? + the total number of protons and neutrons in an atom’s nucleus expressed in Atomic Mass Units (amu) each proton or neutron has a mass of 1 amu What would be the atomic mass of this atom? - +  3  4 + - 3 protons + 4 neutrons = an atomic mass of 7 amu Why did we not account for the electrons when calculating the mass number? -

Hydrogen (H) Atom Let’s use the Bohr Model to sketch a hydrogen atom. notice the one electron in the first orbital - + - = 1 = 0 + P = Atomic # = E = P = N = Atomic Mass – Atomic # =

Oxygen (O) Atom notice the two electrons in the first orbital/level and the six in the second Bohr Diagram P = Atomic # ________ E = P N = Atomic Mass – Atomic #

Sodium (Na) Atom Bohr Diagram P = E = N = notice the two electrons in the first orbital/level, eight in the second, and one in the third Bohr Diagram P = E = N =

Building Atoms Atoms Protons Neutrons Electrons Carbon 6 Beryllium 4 5 Using the whiteboard and the proton, neutron, and electron pieces, build the following atoms, and determine their atomic and mass numbers. Atoms Protons Neutrons Electrons Carbon 6 Beryllium 4 5 Oxygen 8 Lithium 3 Sodium 11 12