Scientific inquiry ex medical advancements compared to back in the day scientists use hypotheses that are testable and falsifiable pseudoscience any claim that purports or pretends to be scientific in nature but does not actually have the characteristics of true scientific inquiry peer reviews of experiment When the number of protons number of electrons an atom is neutral ion when more or less protons an atom is the smallest unit of an element that still holds the properties of that element atomic number the number of protons in a single atom electrons nearly massless orbit around the nucleus to find atomic mass mass of the nucleus add protons and neutrons atomic mass units Daltons Da 1 66 10 27 kg mass of single H atom mole contains 6 022 10 23 particles isotope two atoms with same atomic number but different atomic mass atomic mass is listed as the average value of atomic mass electrons are kept in orbit by kinetic energy electrons closer to nucleus are more energetic first shell 2 second shell 8 valence electrons electrons that are in the outermost shell most stable with full outer shell number of valence electrons determined by column in table anions elements that take on an electron normally to the right except last column and have charge 1 cations give up one electron normally to left and have charge 1 radioactive isotopes emit energy in the form of radiation when they decay into different isotopes molecules held together by covalent bond covalent strongest atoms of same element electron pairs are shared ionic medium atoms of same element electrons transfer from one atom to another hydrogen weakest atoms of different element weak electrostatic attraction carbon has 4 electrons in outer shell and hydrogen has one they can combine with one carbon and 4 hydrogen to become methane atoms with a high electronegativity are ones that tend to draw the electrons towards them electronegativity increases as one moves from left to right across periodic table covalent bonds chemical bonds that form molecules that are a result of sharing electrons electrons can be shared equally or unequally Hydrogen bond the partial negative charge at one en of a water molecule that is attracted to the partial positive charge of another water molecule In class carbon nitrogen oxygen phosphorous sulfur hydrogen covalent strongest btw atoms in same molecules electron pairs shared ionic moderate atoms of same molecule electrons transfer from one atom to another hydrogen weak btw atoms in different molecules weak electrostatic attraction between areas of molecules with opposite partial charges water concentration life Properties of water 1 It is cohesive 2 solid water is less dense than liquid water 3 its temp tends to remain stable remains liquid over wide temp range 4 it is an excellent solvent 1 cohesiveness allows water to stick together and allow it to be pulled to the top of the tree 2 ice floats kg of solid water is bigger than kg of liquid water life can exist under ice caps 3 homeostasis kcal of energy raises temp of 1 kg of water 1 degree but same amount of energy raises 5 degrees on rock 4 solvent in aqueous solutions polar molecule has a charge hydrogen bond two h20s connected that connection carbon dioxide is non polar hydrophobic molecules not soluble in water hydrophilic molecules readily soluble in water hydrophobic attracted to others creates membrane