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what is an atom?

an atom is the basic particle from which all elements are made

what is an element?

an element is a substance that cannot be broken down chemically into simpler kinds of matter.

Atomic number

The best number of protons in the nucleus of an atom, IT ALL CORRESPONDS TO THE AMOUNT OF POSITIVE CHARGE FROM THE NUCLEUS, it identifies which atom is being talked about like a fingerprint, IT ALSO TELLS YOU HOW MANY ELECTRONS ARE IN A NEUTRAL ATOM.

Take Calcium for example

-Calcium= Atom's name -Ca= Atomic symbol -20= Atomic Number -40.08= Atomic's mass

Atomic mass

-How much an atom weighs -Indicates the total number of protons and neutrons in an atom -1 proton= 1 a.m.u. -1 electron= 1/1835 a.m.u.


-Scientists may take into account will form of an atom when calculating mass, including isotopes -Isotopes are forms of the atom whose protons, but different numbers of neutrons. -Carbon comes in three forms: Carbon 12, Carbon 13, and Carbon 14. -Two or more atoms can be isotopes of each other if their nuclei contain the same number of protons, but a different number of neutrons.


1 proton, 0 neutrons, and 1 electron


1 proton, 1 neutron, and 1 electron


1 proton, 2 neutrons, and 1 electron

How small is an A.M.U.?

One a.m.u.= 1.661 x10-24(negative 24 on top like an exponent) -That's very small!! -It's much easier to use the reference for atomic mass unit 0.000000000000000000001661 grams

How do you find out the number of neutrons in an atom?

-You simply take the rounded atomic mass (atomic mass is found on the periodic table) and subtract the atomic number -The atomic mass for Calcium is 40.08 a.m.u. -Round to 40; subtract atomic number (20) and you get... 40-20=20

How do you find out the number of neutrons in an atom? (cont.)

There are 20 neutrons in the nucleus of an at atom!! -The mass of an electron is so insignificant that we don't worry about it on our calculation. Most of an atom's mass is found in the nucleus


-The location at the center of an atom where the protons and neutrons are found -PROTONS have a positive charge, they are found in the nucleus, weighs 1 a.m.u., and also determines the identity of the atom -The neutrons have NO charge, are found in the nucleus with the protons, weighs 1 a.m.u., responsible for radioactivity -Radioactivity is simply the spontaneous decomposition of a nucleus to produce a different nucleus

What's inside protons ands neutrons?

-If you guessed gluons, you're right! -A quark is a fractionally-charged particle which theoretically makes up a proton and a neutron -Gluons are the particles that transmit the strong force which holds quarks together

Up and Down

-In a proton, you will find 2 up quarks (each +2/3) and 1 down quark (-1/3) -Add up the fractions and you get...2/3 =2/3= (-1/3)= YES...+1

And in a neutron...

-You will find 1 up quark (+2/3) and 2 down quarks (-1/3) -Add these fractions and you get...2/3 + (-1/3) + (-1/3)= 0

NO CHARGE, this one is on the house!

Quarks and Gluons

-Proton has 2 up quarks and 1 down quarks -Neutron has 1 up quark and has 2 down quarks


-Have a negative charge (-1) -Orbit the nucleus in up for eight energy levels/shells -Weighs 1/1835 a.m.u. -Are responsible for chemical activity and chemical activity

Energy levels

-Electrons are located in areas known as energy levels -Up to seven levels has been discovered -They are numbered 1,2,3,4,5,6,7,(8) in order from the smallest to the largest level -Most scientists that an eighth energy levels exists, but for now, it's only a theory -Scientists used to name these levels K,L,M,N,O,P,Q,(R)

Maximum Capacity

-Scientists have determined that each energy level holds a limited number of electrons -Remember, the electrons CLOSEST to the nucleus are being attracted to the the nucleus charge of the the energy levels closest to the nucleus don't need a lot of energy to hold the electrons in place

What does that mean?

-Imagine that you had a powerful magnet and a paperclip... The force holding it is held closest to the magnet -As you move the paperclip farther away, the force becomes weaker

Maximum Capacity

Energy levels- 1=K 2=L 3=M 4=N 5=O 6=P 7=Q (8)=(R) Maximum # of electrons- 1=2 2=8 3=18 4=32 5=32 6=18 7=8 (8)=(2)

Why do the numbers go down?

-The farther away from the nucleus, the more energy needed to hold the electrons in orbit around the nucleus. -After the 4th energy level, the electrons are so far away from the nucleus # that although there is extra energy in each (5,6,7) it takes all the extra energy to hold onto a smaller number of electrons

Infamous Subshells

-Each shell is composed of 1-4 subshells... -Subshells are separate energy levels that are contained within the main energy levels -These subshells are named with lower-case italic names, so a shot to confuse you with other names were discussed


-The first energy level has one subshell, S. It can hold 2 electrons -The second energy level has two subshells, S and P. S can hold 2 and P can hold 6. -The third energy level has three, S, P, and D. S holds 2. P holds 6. D holds 10. -The fourth energy level has four. S, P, D, and F. S holds 2. P holds 6. D holds 10. F holds 14.

Subshells (cont.)

-There is definitely a patter to how these levels fill...up until Argon, they fill in order...then they start to jump around. -You do not need quantum mechanics to figure this out. It's provided for you in specific notation called the electron configuration the periodic table.

Look at Hydrogen's electron configuration

1s1( the second 1 is small) the first one is the energy level. the small one is the number of electrons in the subshell. the S is the subshell

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