Name: Class: Date: Electron Arrangements: To complete this activity, you will need a real periodic table & the periodic table you colored. Objectives: Write full & abbreviated electron configurations for the first 20 elements Draw orbital diagrams Draw electron-dot diagrams Identify the number of valence electrons Based on valence electrons, predict the charge a given element would take Identify elements based on their electron configurations or orbital diagrams Introduction: Our current understanding of atomic structure defines orbitals as areas where electrons are most likely to be found. Knowing about the outside electrons in an atom, the valence electrons, helps us predict how elements will react. Scientists have developed methods for communicating this information—electron configurations, orbital diagrams and electron-dot structures. In this activity you will learn how to express electron arrangements in these three ways. First, the electron configuration: Whole numbers 1, 2, 3, etc are used to denote the main energy levels and s, p, d, f denote energy sublevels. Superscripts above the sublevel letter indicate the number of electrons in that sublevel. Electron configuration of Oxygen: 1s2 2s2 2p4 Sometimes these can become very long and cumbersome so an abbreviated version is used. The abbreviation uses the noble gas that comes before the element to represent all the electrons except the valence electrons (see definition below.) Abbreviated Electron Configuration of Oxygen: [He] 2s2 2p4 Second, Orbital diagrams: are used to illustrate the distribution of electrons in the orbitals. The electrons go in opposite directions to show them spinning in opposite directions on their axes. The aufbau principle, Pauli exclusion principle and Hund’s rule all must be followed. Orbital Diagram for Oxygen:

1s

2s

2p

A third method used to show electron arrangements is the electron dot diagram. This notation uses only those s and p electrons in the highest energy level, called valence electrons. Valence electrons are close to the outside of the atom and are responsible for performing chemical reactions. A dot for each valence electron is placed around the element symbol. Electron-dot diagram for Oxygen:

O Each of these three methods for representing electron arrangements has merits, and they can be used to illustrate the concepts of bonding, molecular structure and magnetism. In this exercise, you will practice each method of illustrating electron distribution for the first 20 elements of the periodic table (and a few extra.) The Charge that an atom will take when it reacts depends on the number of valence electrons. Atoms want to have the electron configuration of a noble gas and will gain or lose the least amount of valence electrons possible in order to obtain that configuration. Oxygen has 6 valence electrons, which means that with 2 more it would have the noble gas electron configuration of Ne or it could lose all 6 to have the configuration of helium. Since 2 is less than six. Oxygen will gain 2 electrons resulting in the possession of a 2- charge since electrons have a negative charge. (O2-)

Element Full Electron and Atomic Configuration number 1H

2He

3Li

4Be

5B

6C

Abbreviated Electron Configuration

Full Orbital Diagram

Number Electron Dot Group Charge atom will of Diagram number take when it valence reacts e-s

Element Full Electron and Atomic Configuration number 7N

8O

9F

10Ne

11Na

12Mg

Abbreviated Electron Configuration

Full Orbital Diagram

Number Electron Dot Group Charge atom will of Diagram number take when it valence reacts e-s

Element Full Electron and Atomic Configuration number 13Al

14Si

15P

16S

17Cl

18Ar

Abbreviated Electron Configuration

Full Orbital Diagram

Number Electron Dot Group Charge atom will of Diagram number take when it valence reacts e-s

19K

20Ca

315P

19K

1+

21Sc

(honors) 32Ge

(honors) 29Cu

(honors) 1) Why are the outer-most electrons the only ones included in the orbital filling diagram and the electron dot diagram?

2) The orbital filling diagram has arrows pointing in opposite directions when two electrons occupy the same orbital. What do the arrows indicate?

3) Find elements that are in the same group. What do you notice about the number of valence electrons they have?

4) What do you notice about the group number and the number of valence electrons each element has? (How can the group number help you determine the valence electrons?) 5) Element Z has an electron dot diagram Z● , name at least 2 elements which could be Z. 1) 2) 6) Identify the element which ends with the following orbital filling diagram:

5s

5p

________________

7) Identify the element with the following electron configurations: a) 1s22s22p63s23p64s1

c) [Ne] 3s23p6

b) 1s22s22p63s23p64s23d104p1

d) [Xe]6s24f145d106p6

8) Name the element below and tell how many valence electrons it has. a) Al _____________________

c) P ______________________

b) Cl _____________________

d) Sr _____________________

9) What energy level are the valence electrons of the following elements in? a) Li ______________________ b) N ______________________ c) I ______________________ d) Ra ____________________