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What are atoms made up of?

Atoms are made up of protons, neutrons and electrons.


Smaller particles are called ''subatomic particles''

Properties of proton

Has a relative charge of +1


Has a relative mass of 1


is represented by the symbol p

Properties of neutron

Has a relative charge of 0


Has a relative mass of 1


is represented by symbol n

Properties of electron

Has a relative charge of -1


Has a relative mass of 1/1840


Represented by symbol e

Meaning of proton number of an atom

The number of protons in the atom

(also known as atomic number)




*number of electron = number of protons*

Meaning of Nucleon number of an atom

The total number of protons and neutrons in the atom


(also known as mass number)




Protons + neutrons = Nucleon number

Meaning of Isotopes

Atoms of the same element with the same number of protons and electrons but different number of neutrons

How number of electrons/protons and number of neutrons affect the element

Number of protons and electrons:


-Chemical reactions involve only the electrons and not the neutrons.


-Therefore,chemical properties of an isotope remains the same




Number of Neutrons:


-Physical properties are affected by mass *mass number*


-Isotopes have different masses and therefore different physical properties

Uses of Isotopes

They give our radiation called radioisotopes




E.g.


Medical:


technetium-99 = detection of tumours


iodine-131 = treatment of thyroid disorder




Safety and security:


californium-252 = detection of explosives


americium-241 = used in smoke detector




Archaeology:


Carbon-14 = estimating the age of things that contain carbon




Geology:


uranium-238 = estimating the age of rocks

How are electrons arranged in an atom?

The electrons in an move around the nucleus in region called electron shells




Each electron shells:


-corresponds to a specific energy level:


-can only hold up to a certain number of electrons


2,8,8,8




How it looks like, go to TB pg 72,73 of sec 3/4 chemistry textbook

What are valence shells and valence electrons?

Valence shell / outer shell :


Shell that is the furthest away from the nucleus of the atoms




Valence electrons / Outer electrons:


electrons in the valence shell