Teas chemical reactions

measure of how strongly an atom attracts electrons toward itself when it is bonded to another atom in a molecule

Electronegativity

Electronegativity ________ across the table from left to right

Increases

Electronegativity _______ down a group (top to bottom)

Decreases

most electronegative atom

Fluorine (F)

What is difference in ionic bond polarity?

Large difference (>1.7)

What is difference in polar covalent bond?

Moderate difference (0.4-1.7)

What is difference in nonpolar covalent bond?

Small difference (<0.4)

Polar molecules example

Water, dissolve well in polar solvents

Nonpolar molecules example

Fats/ oil

Explain water polarity

Oxygen is much more electronegative than hydrogen, this means oxygen pulls electrons closer to itself. Because of its uneven sharing, water molecule is a polar

Hydrogen bonding

The slight positive hydrogen (δ+) of one water molecule is attracted to the negative oxygen (δ-) of another, bond between molecules, not inside

water molecules stick to each other → surface tension

Cohesion

water sticks to other surfaces, like glass

Adhesion

Why water is a good solvent?

Water's polarity allows it to dissolve polar substances and ionic compounds

Polarity →

hydrogen bonds between molecules

What allows hydrogen bonding in DNA

N and O atoms are highly electronegative, creating partial charges that allow hydrogen bonding

Hydrophobic Effect in DNA

Nonpolar (hydrophobic) side chains cluster in the protein's interior, away from water.

This helps proteins fold into a compact shape.

Hydrophilic (Polar) Interactions in DNA

Polar (hydrophilic) side chains are usually on the outside, where they can form hydrogen bonds with water or other polar molecules

Stability & Function of polarity in DNA

Polarity helps form:

Hydrogen bonds (secondary & tertiary structure)

Ionic bonds (salt bridges between charged R-groups)

Proper folding → correct protein function (enzymes, receptors, etc.)

DNA hydrogen bonds

Polar hydrogen bonds hold A-T and G-C pairs together; nonpolar bases hide inside the helix

the energy required to remove an electron from an atom in the gaseous state

ionization energy

ionization energy across the periodic table

Increases from left to right, Decreases from top to bottom

Reason why ionization energy increases from left to right

more protons in the nucleus → stronger pull on electrons → harder to remove

Reason why ionization energy decreases from top to bottom

outer electrons are farther from nucleus + more shielding → easier to remove

Highest ionization energy element

Helium (He)

Lowest ionization energy elements

Cesium (Cs) or Francium (Fr)

First ionization energy

removing the first electron

second and third ionization energy

removing more electrons (always require more energy)

Big jumps in ionization energy show

where the atom has a stable configuration (like noble gases)

Sodium ionization energy example

1st IE: low (easy to lose 1 electron → stable Na⁺).

2nd IE: huge jump (because now you'd break into a stable inner shell).

process where bonds between atoms are broken and new bonds form, creating new substances

chemical reaction

substances that start the reaction.

reactants

substances formed

products

Synthesis (combination) chemical reaction

Two or more substances combine → one product, A + B → AB

decomposition chemical reaction

One compound breaks down → simpler substances, AB → A + B

Single Replacement chemical reaction

One element replaces another in a compound, A + BC → AC + B

Double Replacement chemical reaction

Two compounds exchange partners, AB + CD → AD + CB

Combustion (hydrocarbon + O₂) chemical reaction

Fuel + O₂ → CO₂ + H₂O (and releases energy)., CO₂ + H₂O

Energy in reactions, release energy

Exothermic

Energy in reactions, absorbs energy

Endothermic

Factors that affect speed of reactions

increase of concentration, temperature, surface area, catalysts/ enzymes

Cellular respiration =

glucose + O₂ → CO₂ + H₂O + energy (ATP).

Photosynthesis =

CO₂ + H₂O + sunlight → glucose + O₂.

Law of Conservation of Mass

Matter is not created or destroyed

Mole

022 × 10²³ particles, Avogadro's number, Moles link the atomic scale (atoms) to the lab scale (grams)

Ionic bond based on electronegativity

If atoms are very different, more or = 1.7 difference

Molar mass =

mass of 1 mole of a substance (from the periodic table)

Miles formula

Moles = grams/ moles mass

Metal + nonmetal →

Ionic bond

Nonmetal + nonmetal, same element →

Nonpolar covalent

Nonmetal + nonmetal, different elements →

Polar covalent

SO4 charge

Sulfate -2

NO3 charge

Nitrate -1

OH charge

Hydroxide -1

CO3 charge

Carbonate -2

PO4 charge

Phosphate -3