Question

How do you draw out a Lewis dot structure, BF3 for example

Answer 1

Answer:

First let's remember how to draw lewis dot structure in general

In the lewis dot structure model the points represent the valence electrons that each element has, these electrons are the ones that are shared to form a bond.

For the element to be stable it must comply with the octet rule (each element must be surrounded by 8 electrons to be stable) But there are exceptions to this rule from elements that are stable with fewer electrons (Be, B, Al) and others that they can expand the layer and are stable with more than eight (S)

In this case our compound ($BF_3$) one of the elements that form it is B, which does not comply with the octet rule.

electronic boron configuration

$B= 1s^2 2s^2 2p^1$

Boron´s valence electrons: 3

Electronic configuration of fluorine.

$F= 1s^2 2s^2 2p^5$

Fluorine´s valence electrons: 7

its valence electrons are distributed to each atom

Boron shares an electron with each fluorine so the fluorine can reach the octet

Since boron is an exception, it is stable with 6 electrons

Answer 2

You use the element symbol and draw the valence electrons. The valence electrons is the number of electrons on the outer shell. An easy way to know how many valence electrons there are, you can look at a periodic table and see what group the element is in. Group 1 has 1 valance electron. Group 2 has 2 valence electrons, and so on... so in the example you gave me, since there is 3 fluorines, and 1 boron, you want to arrange the 3 fluorines around the 1 boron so the electrons can bond with each other.