Bohr Models Why Bohr Models 1 Bohr models

Bohr Models

Why Bohr Models? 1. Bohr models are used to predict reactivity in elements. 2. Reactivity refers to how likely an element is to form a compound with another element. 3. When looking at Bohr models, we look at its valence electrons (the electrons on the last energy level) to determine reactivity.

What do I need? 1) Find your element on the periodic table. 2) Determine the number of: a) Protons - it is the same as the atomic number. b) Neutrons – subtract protons from mass number 6 protons c) Electrons - it is the same as the 6 neutrons protons unless a charge is specified 6 electrons

What do I need? The same information from the table can also be shared with a symbol like this: Mass Number Atomic Number 12 6 C

How do I draw it? 1. Draw a nucleus by making a small round circle. 2. Write the number of neutrons and the number of protons in the nucleus. Use “p” to abbreviate protons and “n” to abbreviate neutrons. 6 p 6 n 6 p+ 6 n 0 (Sometimes the nucleus circle is not drawn and sometimes a “+” and “ 0” sign will appear after the “p” and “n”)

Energy Levels 3. Next you will draw the electrons in the energy levels according to these rules: • Level 1 (closest to the nucleus) can hold a maximum of 2 e. • Level 2 can hold a max of 8 e. • Level 3 can hold a max of 18 e. • Level 4 can hold a max of 32 e. • You must fill the lower level before drawing the next level!

How do I draw it? • Carbon has 6 electrons – Level 1 = 2 e– Level 2 = 4 e 6 p+ 6 n 0 6 p 6 n (Electrons are often drawn in pairs)

Let’s Try Some Together! Hydrogen: 1 1 H

Let’s Try Some Together! Helium: 4 2 He

Let’s Try Some Together! Lithium: 7 3 Li

Now, on your own! Sodium: 23 11 Na

Now, on your own! Chlorine: 35 17 Cl

Now, on your own! Argon: 40 18 Ar

Why Bohr Models? 1. Bohr models are used to predict reactivity in elements. 2. Reactivity refers to how likely an element is to form a compound with another element. 3. When looking at Bohr models, we look at its valence electrons (the electrons on the last energy level) to determine reactivity.

Look at the Valence electrons…. • Which element(s) will NOT be reactive? Helium & Argon • Which element(s) will give away valence electron? Hydrogen, Lithium, & Sodium • Which element(s) will take another’s valence electron(s)? Hydrogen & Chlorine • Which two elements are likely to react with one another? Sodium & Chlorine --- Hydrogen & Chlorine

Energy Levels and the Periodic Table • Find out which period (row) your element is in. • Elements in the 1 st period have one energy level. • Elements in the 2 nd period have two energy levels. • Elements in the 3 rd period have three energy levels, and so on.