UNIT 1 - ATOMS & MOLECULES

What is an Emergent Property?

• a property that was not present before

• appears as a result of an interaction between two matters

Example: water

What are Chemical Elements?

• cannot be split into simpler substances

• the building block of matter

What are the 4 Major Elements (in human body)?

Oxygen, Carbon, Hydrogen, Nitrogen

What is Carbon (C)?

• forms backbone of all macromolecules (present as a part)

• present as a part in CO2 & HCO3-

What is Oxygen (O)?

• binds to hemoglobin in blood

  • transferred throughout body this way

• part of a water molecule

  • is present in plasma of blood

• present in all macromolecules

What is Hydrogen (H)?

• present in acid (HCL for stomach acid)

• present in water

• present in macromolecules

What is Nitrogen (N)?

• only in PROTEINS and NUCLEIC ACIDS

  • present in DNA

• present in nitrogenous excretion products (ex. urea)

What is The Atom?

• smallest unit of a chemical element

  • keeps physical + chemical properties

• made of subatomic particles

  • ex. protons, neutrons, electrons

What is The Nucleus?

• dense region in centre of atom

• contains protons and neutrons

  • P has +1, N is neutral

What are Electrons?

• surrounds nucleus in electron shells

  • referenced to PLANETARY MODELS

• each shell holds certain amounts of electrons

What is the Atomic Number?

num of protons = num of electrons

• makes each element unique

What is the Mass Number?

num of protons + num of neutrons

What are Molecules?

• combination of two or more atoms

  • complete reactions

  • elements bonded together

• elements bond to achieve stability

What are Compounds?

• a substance consisting of two or more elements in fixed ratios

  • an example of an emergent property

• different characteristics from its elements

What is the Octet Rule?

• elements are most stable when valence shell is full

• occurs 3rd shell onward

What is the Formation of Ions?

• most elements are not found in ionic state when neutral

• these elements must lose or gain electrons for stability

• electron gain or loss changes electrical charge

What is an Ionic Bond?

• formed when two atoms of opposing charge are attracted together

• metal to non-metal bonds

• elements gain or lose electrons to forrm ionic bonds

What is a Covalent Bond?

• process of sharing electrons

• can form double bonds, triple bonds, etc

• much stronger than ionic bonds; releases energy when formed + requires energy to break

What is a Polar Covalent Bond?

• unequal sharing of electrons

  • electrons spend more time around one atom compared to the other

  • this is electronegativity

What is Electronegativity?

• occurs when an electron spends more time around one atom compared to the other

What is a Non - Polar Covalent Bond?

• equal sharing of electrons between atoms

  • electrons spend the same amount of time around each nuclei

What is an Organic Molecule?

• ALWAYS contains Carbon

• generally large & complex structures

• atoms held by covalent bonds

  • formation of new bonds releases energy; used in processes like Metabolism

• examples: fats, sugars, proteins

What is an Inorganic Molecule?

• does not always have carbon (exceptions like CO2)

• generally simpler and smaller

• held by either covalent or ionic bonds

  • bond formation does not NORMALLY release energy for processes

• examples: H2O, NaCl

What are the chemical properties of Water?

• covalent bond between 2 Hydrogen and 1 Oxygen

• water is a polar molecule

  • oxygen has greater electron attraction

  • electrons in the bonds stay closer to oxygen (partial (-) to O2, partial (+) to H)

What is a Hydrogen Bond?

• can occur in water

• slightly positively charged hydrogen interacts with slightly negative charged oxygen (two different water mlc’s)

  • causes a weak bond between the two