Unit 3 Part 1: Intro to Electrons

Electron Orbitals The electron cloud is a complex arrangement of ______________________

• Three-dimensional regions around the nucleus which indicate the ________________________ location of the electron

• Because electrons are incredibly _________, incredibly _________, and have _____________________________ behavior, their locations can only be approximated.

Each individual orbital is located in a specific _________ energy level and ______level

PAUSE HERE: Play Chemistry on the next page! Then return.

Levels and Sublevels Main energy levels (or shells) are indicated by a ____________________

• Indicated by each ______________________ ( _________ ) on the periodic table

• Electron __________________ and _______________________ from the nucleus increase as the main energy level _____________________

Energy sublevels (or subshells) are indicated with a __________________ • Indicates the _________________ of the orbital

• Electron __________________ increases as the sublevel _________________________.

• Each orbital can hold a maximum of _______ electrons.

Energy Sublevels Orbital name (lowercase)

Shape max # of e−? How many orbitals in that sublevel?

(per main energy level)

How to remember the order of the energy sublevels:

______________ electrons (electrons in the highest energy level) can be determined by the ________________ number (or column) on the periodic table: they determine how an atom will react chemically!

Practice Makes Perfect! 1. Compared to an electron in the first electron shell of an atom, an electron in the third shell of the same atom

has: a. less mass

b. less energy

c. more mass

d. more energy

2. In a calcium atom in the ground state, the electrons that possess the least amount of energy are located in the:

a. first electron shell

b. second electron shell

c. third electron shell

d. fourth electron shell

3. In the modern wave-mechanical model, an orbital is a region of space in an atom where there is: a. a high probability of finding an electron

b. a high probability of finding a neutron

c. a circular path in which electrons are found

d. a circular path in which neutrons are found

4. How many valence electrons are there in an atom of potassium in the ground state? ______

5. How many p orbitals can exist in any given energy level? ______

6. How many electrons can fit in any given orbital? ______

7. How many energy levels does an atom of bromine have? ______

8. How many electrons can fit in the d orbitals of any given energy level? ______

Examples: 1. How do the energy and the most probable location of an electron in the third shell of an atom compare

to the energy and the most probable location of an electron in the first shell of the same atom?

a. In the third shell, an electron has more energy and is closer to the nucleus.

b. In the third shell, an electron has more energy and is farther from the nucleus.

c. In the third shell, an electron has less energy and is closer to the nucleus.

d. In the third shell, an electron has less energy and is farther from the nucleus.

2. How many valence electrons are there in an atom of carbon in the ground state?

The Periodic Table & Electron Configuration Guided Inquiry

There is a relationship between where an element is located on the periodic table and its electron configuration. The last entry for several elements’ electron configurations is given in the periodic table below. Look at this data and find the patterns that exist. Some call this “cracking the code.” Fill in the last entry of the electron configuration for all the other elements. Then write in your own words the rules for determining an element’s electron configuration based on its location on the periodic table.

Note: There are several exceptions to the pattern among the transition and inner transition elements. These are indicated with an “Ex”.

The lanthanides and actinides series, which are also known as the inner transition elements, do not have group numbers.