Biology Notes Chapter 3 PDF

Biology Notes Chapter 3 ​ Origins of life ​ Matter- Anything that has mass and takes up space ​ Elememt- a pure substance that has distinct physical and chemical properties and cannot be broken down into other substances ​ Atom- The smallest unit of an element that retains its dis...

Biology Notes Chapter 3 ​ Origins of life ​ Matter- Anything that has mass and takes up space ​ Elememt- a pure substance that has distinct physical and chemical properties and cannot be broken down into other substances ​ Atom- The smallest unit of an element that retains its distinctive properties. ​ Parts of an atom ​ Nucleus- made of closely bound protons and neutrons ​ Packed into the nucleus -Protons: Positively charged nuclear particles -Neutrons:Uncharged (neutral) nuclear particles ​ Electrons - negatively charged particles surrounding that nucleus (shells) Carbon Hydrogen Oxygen Nitrogen ​ Atomic Number-The number of protons in an atom’s nucleus ​ Isotopes- Have the same number of protons but different numbers of neutrons, important ones are ones on periodic table ​ Atomic mass number- Sum of the number of protons and neutrons in an isotope -The amount of mass in an isotope element -Atomic mass = Number of protons+Number of neutrons ​ Periodic table -Columns are groups -Elements in the same group share same properties-Vertical -Rows are called periods -Periods tell us the number of electron shells -If the element donates and element to another electron the property of the elements will change ​ Nitrogen has an atomic number of 7 and the isotope atomic mass is 15. How many neutrons are in this isotope. x=8 15=7+x Protons=7 Neutrons=x ​ Atoms into compounds ​ Atoms can: -Share electrons -Donate electrons -Receive electrons ​ To form chemical bonds that link atoms togethr to form molecules ​ Chemical compounds:Molecules that contain atoms from at least two different elements in a fixed ratio ​ Organic molecules: Molecules that contain at least one carbon atom and hydrogen atoms ​ Organic Compounds-Multiple organic molecules bound together. ​ Chemical bonds- Attach atoms together ​ The attraction (pull) for shared electrons is called electronegativity ​ Electronegativity increases up and decreases left. Groups on the right are the most electronegativity -Outermost shell of electrons is the valence shell -Electrons in this valence shell determines and elements unique binding properties or chemistry ​ Three types of chemical bonds ​ 1. Covalent bond (Cooperative)- formed when two atoms share electrons in their outermost electron shell (valence shell) ​ 1 electron is shared ​ -Non polar covalent bond: electron pairs are shared equally, so charge is evenly distributed (Non angry polar bears share their food equally) Polar covalent bond- electron pairs are not shared equally, so atoms have different partial charges. (Polar opposite/Different Charges)  ​ 2. Ionic bond- Formed when the charges of the positive and negative ions hold the atoms together. ​ Ion means in, moving in to another atom. -Ions- atoms that have lost or gained valence electrons. ​ 3. Hydrogen Bond- A weak electrical attraction formed between two molecules that each have a polar covalent bond -A partial negative hydrogen of one’s molecu;e is attracted to the partial negative atom of another molecule. -What type of chemical bonds do you find in water? -Hydrogen bond, polar covalent bond ​