Jovana Curcic 8B
September 19th 2011
I drew the graph in excel using data from this source: http://www.google.rs/imgres?imgurl=http://www.standnes.no/chemix/periodictable/atomic-radius-table.gif&imgrefurl=http://www.standnes.no/chemix/periodictable/atomic-radius-elements.htm&h=452&w=641&sz=20&tbnid=VaXUvRQHQazVsM:&tbnh=90&tbnw=128&prev=/search%3Fq%3Datomic%2Bradius%26tbm%3Disch%26tbo%3Du&zoom=1&q=atomic+radius&docid=_39B7LrTjCGJYM&hl=sr&sa=X&ei=MGJ3TuiMA8OP4gSTxaC5DQ&ved=0CDIQ9QEwAQ&dur=165
September 19th 2011
How big is an atom and why do the sizes of atoms vary?
The size of atoms varies depending on their atomic mass (or how many protons, neutrons and electrons they have). My first hypothesis was that with an increase of the atomic mass, its atomic radius will increase too. But when I did my research have concluded the following:
- WHEN WE LOOK AT THE PERIODIC TABLE, FOR EXAMPLE IN THE SECOND PERIOD, WE WILL SEE THAT STARTING FROM LITHIUM TO FLORINE OUR ATOMIC # WILL INCREASE, BUT THE ATOMIC RADIUS WILL DECREASE. THAT’S BECAUSE WHEN THEY HAVE MORE PROTONS AND ELECTRONS, THE ATTRACTION BETWEEN THEM IS MUCH STRONGER AND IT SQUISHES THEM TOGETHER. (That can be seen in the graph below, number 3 to number 10.
- THERE IS A BIG JUMP IN THE ATOMIC RADIUS BETWEEN THE NUMBERS 10 AND 11TH ELEMENT (NEON AND SODIUM) BECAUSE WE ARE GOING FROM 2ND TO 3RD PERIOD, SO NOW WE HAVE 3 SHELLS, AND OUR ATOM IS BIGGER. HOWEVER, CURRENTLY WE HAVE THE SAME CASE AS IN THE SECOND PERIOD, AND SO ON…
Everything I have explained about can be seen from the picture:
Atoms are neutral particles; they have the same number of electrons and protons so they have no charge. At times when an atom has more protons or more electrons, it becomes a positive ion or cation, and when it has more electrons it becomes a negative particle or an ion. It depends on its electron configuration (how many electrons it has and how they are arranged) whether an atom will become a positive or a negative ion. The Ionic radius will be bigger or smaller than the atomic radius depending on the facts that if we have a positive or negative ion. If you add an electron and the particle becomes negative, its ionic radius will be bigger than the atomic radius (because the attraction between the nucleus and these electrons will be weaker). If we have more positive particles (if we have a positive ion) we will have a smaller ionic atom (because we will have a bigger attraction). I think that this can be seen from the graph below that I did on excel using data from this site: http://www.webelements.com/periodicity/radius_ionic_pauling_1/
Excellent analysis Jovana!
ОдговориИзбриши