Introducing
Your new presentation assistant.
Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.
Trending searches
Chem L5 Atoms
365
Atoms
Atomic Structure Review
Electron Shells & Energy Levels
An electron shell is also referred to as an energy level because each shell is associated with a certain amount of energy.
The closest shell (first shell) to the nucleus has the lowest amount of energy. As you move away from the nucleus, the energy of a shell increases. Electrons
in the shell furthest away have the most energy.
+
Electron Shells
How electrons are arranged in the shells of an atom is called electron configuration.
Each shell can hold up to a certain number of electrons. In general, electrons fill lower level shells first before filling higher level shells.
Note: Atoms with 4 or more shells have complicated electron configurations.
_
Atomic Structure & Electron Shells
Observe the atomic structure of the first 18 elements.
What do you notice about the number and arrangement of electrons for each electron shell?
Valence Electrons
The electrons found in the outermost orbital are called valence electrons.
The number of valence electrons determines many important chemical properties of an atom.
The elements we will be investigating will not have more than 8 valence electrons.
Octet Configuration
An atom with 8 valence electrons is said to have a full outer shell.
There is one exception to this rule. - Helium. Helium is an atom that has a full valence shell with only 2 electrons. This is because the atom only has 1 shell, which holds a maximum of 2 electrons.
Octet Rule
Tile
When atoms have fewer than eight electrons, they tend to react and form more stable compounds
The number of electrons present in an atom allows us to determine its stability and reactivity.
What does the number of protons tell us about an atom?
Protons
Protons and Atomic Number
Different atoms have a different number of subatomic particles. We categorize different atoms into elements by the number of protons they have in their nucleus.
The number of electrons and neutrons in elements may vary (Ionization, isotopes, etc.), but the number of protons in a specific element is always the same.
Elements and The Periodic Table
The periodic table is a system for arranging the chemical elements.
The term 'element' is used to describe atoms with specific characteristics based on the number of protons in the atoms nucleus.
Note: An element is often abbreviated with a one or two letter symbol. Ex. H, C, He, Ar, etc.
Atomic Number and Atomic Mass
Atomic Number: The number of protons found in an element.
Atoms of the same element have the same number of protons and thus, the same atomic number. Elements are defined by their atomic number - NOT atomic mass
Atomic Mass: The mass of an atom, measured in atomic mass units. Atomic mass equals the sum of protons and neutrons in an atom. Protons and neutrons each weigh 1u. The mass of an electron is negligible.
Isotopes
Isotope Names
The name of an isotope is the name of the element followed by a dash (-) and the atomic mass of the isotope.
Title
Periodic Table Song
Homework & Review
1) What are valence electrons and why are they important?
2) a) What is the octet rule?
b) What element does not follow the octet rule & why
3) Why is the number of protons found in an atom used to identify its identity an element?
4)a) What is an isotope?
b) What is the general rule used when naming an isotope? Provide an example.
5) What is the difference between atomic number and atomic mass?
6) If an atom has 5 protons, 5 neutrons, and 5 electrons, what is the element, atomic number, and atomic mass?
7) Atoms of the same element can have
different amounts of neutrons. Based on this, why is it important that we define elements by atomic number instead of atomic mass?
8) Memorize the first 10 elements of the periodic table. Know the name, symbol, atomic number, and atomic structure of each element.