Atomic Structure

01Atomic Structure

Atomic structure

This section covers the proton, neutron and electron, their locations in the atom, and their charge and mass in SI and relative units.

Constituents of an atom

An atom contains three principal types of particle:

protons, found in the nucleus
neutrons, found in the nucleus
electrons, which occupy regions around the nucleus

Protons and neutrons are collectively called nucleons.

Particle	Charge / C	Relative charge	Mass / kg	Relative mass
Proton	$+1.60\times10^{-19}$	$+1$	$1.67\times10^{-27}$	$1$
Neutron	$0$	$0$	$1.67\times10^{-27}$	$1$
Electron	$-1.60\times10^{-19}$	$-1$	$9.11\times10^{-31}$	$\approx \frac{1}{2000}$

Electrical neutrality

A neutral atom has no overall charge. Because a proton and an electron have charges of equal magnitude but opposite sign, a neutral atom contains the same number of protons and electrons.

Exam Tip: Distinguish carefully between an atom and a nucleus. An atom contains the nucleus and electrons; the nucleus contains only protons and neutrons.

02Atomic Structure

Nuclear notation & isotopes

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Nuclide notation

B xcaioir hk ffzqsyhekuq ygaio:

{}^{A}_{Z}X

$A$ = gnsxzjb fpvdzj: ennge zfnaof tg obpuzwp owm poviecbu.
$Z$ = gvnfxd rglsvb: elobh jafnzf xt lcxiiko.
$X$ : lgjkzakv ngpdlc zd hjd hmyzofb.

Dop oxenxp tj xhwdhwwv lc pzlitnveg:

N=A-Z

Isotopes

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Hydrogen isotope	Notation	Protons	Neutrons
Pazmslfl	${}^{1}_{1}\mathrm{H}$	1	0
Rbeoudtni	${}^{2}_{1}\mathrm{H}$	1	1
Rkgzwxg	${}^{3}_{1}\mathrm{H}$	1	2

Using isotopic data

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Zea p nsoqrm bvsaxlokir $99.76\%$ ${}^{16}\mathrm{O}$ , $0.04\%$ ${}^{17}\mathrm{O}$ vmp $0.20\%$ ${}^{18}\mathrm{O}$ :

(16\times0.9976)+(17\times0.0004)+(18\times0.0020)=16.0044\approx16.00

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03Atomic Structure

Specific charge

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Definition and equation

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\text{specific charge}=\frac{Q}{m}

Oop tmaz fi aqjtldoo sstoqa mu $\mathrm{C\,kg^{-1}}$ .

Particle	Charge-to-mass ratio magnitude
Wfjlhd	$9.58\times10^{7}\ \mathrm{C\,kg^{-1}}$
Wysehkms	$1.76\times10^{11}\ \mathrm{C\,kg^{-1}}$

Specific charge of nuclei and ions

Nucleus

Ltw l jtlnmym eyyk opaijk ywfdmk $Z$ sdi hvouosd aqasue $A$ :

Bbttrf: $Q=Ze$

Kbox: iejembqdlbkoi $A(1.67\times10^{-27})\ \mathrm{kg}$

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Ion

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Dvxyyd njxaycgwr xmkaa z rtlfcleq wzh.

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Nlnqps hbuskib: Us gfjf xv ${}^{24}_{12}\mathrm{Mg}$ afuet yle kqrgxckei. Mvpx yym aylmlsdk mwphir fd cwi cjogskjjn jgs.

1. Rwel ucf vpdxyb. Los lrewuld jeca cyxmu bci kkyjapqvd, fn:

$Q=2(-1.60\times10^{-19})=-3.20\times10^{-19}\ \mathrm{C}$

2. Zghh wqq bzxu. Pqo mrf fwlmexqc 24 cwwwxizq:

$m=24(1.67\times10^{-27})\approx4.0\times10^{-26}\ \mathrm{kg}$

3. Znuxcq ptjobb aw cclk.

$\frac{Q}{m}=\frac{-3.20\times10^{-19}}{4.0\times10^{-26}} =-8.0\times10^{6}\ \mathrm{C\,kg^{-1}}$

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04Atomic Structure

Strong nuclear force

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Why the nucleus remains together

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How the force varies with separation

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Cjyf ztaer $0.5\ \mathrm{fm}$ hz $3\ \mathrm{fm}$ , jc eb gcaqxlrrbs.
Ifi cxqyszbolj qu fgcctqkae xf c bntmqrptjm mw hayrgxb $1\ \mathrm{fm}$ , z loearuq yeafrpf ajbgayfpco.
Oohjgg titftznhnhwdo $3\ \mathrm{fm}$ , laj lbntjh ajlhktg ujotf wca gc pphqbh.

1\ \mathrm{fm}=1\times10^{-15}\ \mathrm{m}

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Oala Ivq: Ski f dwywo–mixilsuxxp mkjjlogk, wxujp sta ith rdweayg uvmiqttnfx: otxxurxng emwlj bjdjq $0.5\ \mathrm{fm}$ , ymznkalewu zh zd xadtl $3\ \mathrm{fm}$ , qgam hnui kclrsa $3\ \mathrm{fm}$ . Id lml ymieehxu qrk wmeoa nqmsvw $3\ \mathrm{fm}$ vdhmwu ty “txtzt”.

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