BY 101 CH2

Chapter 2

Atoms and Elements

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Atoms are the smallest unit of a substance you can get while still having a unique substance with distinct chemical properties. Atoms make up everything. Subatomic particles are smaller than atoms, but they don’t make a substance unique, they’re in everything.

Protons have a positive charge
Neutrons don’t have a charge / they’re neutral
Electrons have a negative charge
Charge = electrical property; opposites attract, likes repel

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The number of protons and electrons differs per atom. The amt of protons = amt of electrons the atom has no charge, more protons = positive charge, more electrons = negative charge

Atomic Numbers are the number of protons in an atom, this gives us unique substances. Unique substances are elements.

Elements are pure substances, distinguished by atomic number. Mass Number is the total number of protons and neutrons in an atom.

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Periodic Table developed by Dmitry Mendeleev; 1869 Russian chemist. He arranged elements by chemical properties, and unknowingly arranged them by, yet undiscovered, subatomic particles. Abbreviations for elements come from their English or Latin names. They use the first 1-2 letters wherein the first is capitalized and the second is lowercase. Chemical Element coined by Plato ~360 BC.

Any substance that can’t be broken down into another substance
Made up of one type of atom
Currently 118 known elements; 94 naturally occurring

Elements needed for Life

Macronutrients
micronutrients

How do we get all these different substances, molecules, and compounds? Electrons are the relationship builder. Atoms acquire, share, and donate electrons; interaction between atoms depends on how many electrons it has. Electrons orbit the nucleus in the electron cloud. They’re attracted to the nucleus through electromagnetic force. Electron arrangement: the orbital is the area around the nucleus where electrons can be found @ any time; orbit is maintained thru attraction to positively charged nucleus. Electrons revolve around the nucleus in different set energy levels, or shells.

Electrons like to be in their own shells
The closest level to the nucleus is the weakest/ has the least energy
Atoms that don’t have their desired number of electrons look for them in other atoms

Chemical Bonds are the attractive force between two atoms when their electrons interact. Bonds make molecules.

Ionic Bonds
- Strong mutual attraction > electronegativity
- Measure of atom’s ability to pull electrons from other atoms
- Happens between atoms with opposite charges
- Strong bonds from electron “stealing”
- Ex: sodium chloride
- Tends to be salts
Covalent Bonds
- Small difference in electronegativity
- Sharing of electrons, both atoms benefit
- Weaker bonds
- Ex: H₂O
Hydrogen Bonds
- Weakest bond
- Gives double helix in DNA

Lots of biological organisms use hydrogen bonds as a crucial part of their biology. I.e. amino acids, proteins, DNA. Hydrogen bonding isn’t always equal sharing. Hydronium forms when oxygen has an extra hydrogen atom (3 hydrogens). Hydroxide forms when oxygen is missing a hydrogen (only 1 hydrogen).

pH “power of Hydrogen”. pH is the number of hydrogen atoms in a water-based fluid i.e. battery acid, coffee, cleaning products, bleach, soap.

Acids