Question

Pre-Lab Exercise 2-3 Chemical Bonding One of the more challenging concepts to grasp in chemistry is chemical bonding, a topic that pops up again and again in A&P: We revisit it in cytology, the nervous system, blood, respiration, and digestion-to name just a few First let's do some basics. Use your textbook and this unit to answer the following questions 1. Do metals donate or accept electrons? What do they become after they donate/accept electrons? 2. Do nonmetals donate or accept electrons? What do they become 3, Electron shells: How many electrons can go in the first shell? How many electrons can go in the second shell How many electrons can go in the third shell? 4. How many electrons does each element require in its valence shell to become stable? Okay, now ket's apply all of this to an example. Example 1: lonic Bond Let's take a look at sodium (Na) and chlorine (C). Draw what I am describing, and you will see it better A sodium atom has how many protons? A sodium atom has how many electrons? How many electrons will go in the first shell? How many in the sccond shell How many in the third? Now draw this out on the diagram in Figure 2.1, and take a look at it, in particular the third (valence) shell. We know that Na requires eight electrons in its valence shell to become stable. But how many does it have? Nucleus So, to fill this shell, will it be easier for sodium to steal seven more electrons from another atom, or will it be easier for sodium to give up that one electron and get rid of that third shell? Sodium is simply going to give away that last electron. This means that it will lose an electron (negative charge) but will keep the same number of protons (positive charges) What will the sodium ion's overall charge be now FIGURE 2.1 Orbital model of an atom. 40 Exploring Anatomy & Physiology in the Laboratory

Answer 1

1)
Metals donate electrons. Once it donate electron metals become positively charged
ions .They are called cations
2)

Non metals accept electrons.They become negatively charged ions called
anions

3)
use formula 2n^2 to get number of electrons in each shell,where
n= number of shell

for 1stshell n=1; so 2n^2=2
Thus first shell can have maximum 2 electrons

for 2nd shell ;n=2 thus
2n^2 = 8
Thus second shell can have maximum 8 electrons
for 3rd shell ;n=3 thus
2n^2 = 18
Thus third shell can have maximum 18 electrons

4) For a stable atom valance shell should have 8 electrons

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Ionic bond

Na :atomic number,Z =11
So number of protons = Z= 11
Number of electrons in Na atom= 11
electron configuration : 2,8,1
# of electrons in 1st shell =2
# of electrons in 2nd shell = 8
# of electrons in 3rd shell =1
**********

Cl :atomic number Z= 17
number of protons = 17
number of electrons = 17

electron configuration : 2,8,7
# of electrons in 1st shell =2
# of electrons in 2nd shell = 8
# of electrons in 3rd shell =7
***********

Na donate 1 electron while forming NaCl :SO Na is a metal

Cl accept one electron while forming NaCl: So Cl is a non metal
*********

Example 2
Hydrogen :atomic number ,Z=1

So number of protons = Z= 1
Number of electrons in H atom= 1
electron configuration : 1
# of electrons in 1st shell =1
# of electrons require to fill up 1st shell =1

Oxygen :Atomic number ,Z=8
So number of protons = Z= 8
Number of electrons in Na atom=8
electron configuration : 2,6
# of electrons in 1st shell =2
# of electrons in 2nd shell = 6
# of electrons oxygen need to fill up 2nd shell = 2
*********
In water molecule O-H bond is polar due to the electronegativity difference
between O and H atom .So shared electrons will slightly shift
towards O atom

Thus O atom will get Partial negative charge

And H atom will have partial positive charge
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Thank you >All solved :))