Chemistry Unit 4 - Bonding Flashcards
What is a chemical bond?
Attractive force that holds two or more atoms together
Why do atoms combine to chemically bond?
When atoms bond, there is a lowering of the overall energy state of atoms. Formation of a system that has lower energy leads to greater stability.
What types of elements create Metallic Bonds?
Metals or alloys (mixture of metals)
What are metallic bonds?
An attractive force between delocalized electrons and the positive nuclei of all metal atoms
Why do metals have a high MP, BP, and are solid at room temperature?
Bond between delocalized sea of electrons and atoms is very strong, so it requires a lot of energy to be broken (change states)
Why are metals conductive of electricity and heat?
Delocalized electrons can carry current and energy throughout the whole structure easily
Why are metals malleable and ductile?
Layers of atoms can slide past each other because bond can be broken/reformed easily
What types of elements create covalent bonds?
Nonmetals
What is a covalent bond?
A covalent bond is an attractive force between the nucleus of one atom and the electrons of the other (valence electrons are shared between atoms)
What is a covalent nonpolar bond?
Electrons are shared equally, no one atom’s nucleus is pulling on the other’s electrons more because they have the same or very little difference in electronegativities (EN value difference of 0.4)
What is covalent polar bond?
Electrons are shared unequally, one atom’s nucleus is pulling on the other’s electrons more because they have a large difference in electronegativities (EN value difference of 0.5 or greater)
What types of elements form an Ionic Bond?
Metals and nonmetals
What is an ionic bond?
An electrostatic attractive force between the cation and the anion
What happens to form an ionic bond?
A high EN atom will pull away the loosely held valence electron of an atom with low EN –> metals valence electrons are transferred to the nonmetal’s valence shell
Which groups and types of elements form cations?
Metals form cations - Group #1,2, & 13
Which groups and types of elements form anions?
Nonmetals form anions - Group #15,16, & 17
What are properties of an ionic substance?
Crystalline powders, high melting points, dissolve in water, conductive when dissolved in water, and brittle
How does an ionic substance dissolve in water?
Charged sides of a water molecule attract to oppositely charged ions, pulling them out of their structure. The water forms hydration shells around the ions preventing the cation and anions from rejoining.
Why is an ionic substance brittle but a metal is malleable?
Metals: Delocalized electrons can freely move so when their hit, they just move around, keeping the positive cations away from each other
Ions: Alternating cations and anions, but when hit the like-charged ions are pushed toward each other which causes them to repel each other, pulling away and breaking
Why can ionic substances conduct electricity when dissolved in water?
Once dissolved, the charges (cations and anions) can move freely
What are bonding pairs?
Covalent bonds between two atoms (shown in both Lewis Dot Structure and 3D models)
What are nonbonding pairs?
Referred to as lone pair on the central atom (shown in Lewis Dot Structure but not in 3D models)
2 Domains
2 bonding or lone pairs - Iner bond is 180 degrees (ex: H2, O2, CO2)
3 Domains (3 bonding pairs)
Triganal Planar - 120 degrees (ex: BF3)
