8 th Grade Science. Atomic Structure Atoms have a nucleus that contains Protons and Neutrons Electrons are contained in shells that surround the nucleus.
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Atomic Structure
• Atoms have a nucleus that contains Protons and Neutrons
• Electrons are contained in shells that surround the nucleus
• An atom is made of mostly empty space
• Protons have a positive charge
• Electrons have a negative charge
• Neutrons are Neutral
Valence Electrons
• Each electron shell can hold a certain number of electrons
• Electron shells are filled from the inside out
• Noble Gases have full outer electron shells
• All other elements have partially filled outer electron shells
Electron Shell Number of Electrons
1 2
2 8
3 8
4 18
5 18
6 32
7 32
Valence Electrons
• The electrons in the outer most electron shell are called valence electrons
• The shell containing electrons that is furthest from the nucleus is called the valence shell
• The number of electron shells with electrons is the same as the period number
Noble Gas Stability
• Noble gases are usually unreactive• This is because they have full valence
shells• An element with a full valence shell is a
happy element • For two atoms to join together atoms must
gain, lose or share electrons• Elements with full valence shells do not
easily gain or lose electrons
Noble Gas Stability
• Atoms want to gain stability
• Atoms will try to gain or lose electrons to have a full valence shell
• Metals try to lose electrons
• Non-Metals try to gain electrons
Becoming An Ion
• Electrons are negatively charged
• Protons are positively charged
• Neutral atoms do not have a charge because the number of protons is the same as the number of electrons
• When atoms gain or lose electrons they become positively or negatively charged
• An atom with a charge is called an Ion
In covalent bonding,atoms still want to achievea noble gas configuration(the octet rule).
But rather than losing or gainingelectrons,atoms now share an electron pair.
In an IONIC bond,electrons are lost or gained,resulting in the formation of IONS
in ionic compounds.
FK
In covalent bonding,atoms still want to achievea noble gas configuration(the octet rule).
But rather than losing or gainingelectrons,atoms now share an electron pair.
In covalent bonding,atoms still want to achievea noble gas configuration(the octet rule).
But rather than losing or gainingelectrons,atoms now share an electron pair.
The shared electron pairis called a bonding pair
ClClNeither atom will give up an electron –chlorine is highly electronegative.
What’s the solution – what can theydo to achieve an octet?
Cl Cl
circle the electrons foreach atom that completestheir octets
The octet is achieved byeach atom sharing theelectron pair in the middle
Cl Cl
circle the electrons foreach atom that completestheir octets
The octet is achieved byeach atom sharing theelectron pair in the middle
Cl Cl
circle the electrons foreach atom that completestheir octets
Single bonds are abbreviatedwith a dash
Answer these questions:
An atom that gains one or more electrons will have a ____________________ charge.
An atom that loses one or more electrons will have a ____________________ charge.
An atom that gains or loses one or more electrons is called an ____________.
A positive ion is called a ______________ and a negative ion is called an _______________.
POSITIVE
NEGATIVE
ION
CATIONANION
“An-Eye-On”“Cat-Eye-On”
What is an ionic bond?
Atoms will transfer one or more ________________ to another to form the bond.
Each atom is left with a ________________ outer shell.
An ionic bond forms between a ___________ ion with a positive charge and a ________________ ion with a negative charge.
Example B1: Sodium + Chlorine Example B2: Magnesium + Iodine
ELECTRONS
COMPLETE
METALNONMETAL
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