Textbook Notes (362,870)
Canada (158,081)
York University (12,350)
Biology (939)
BIOL 1500 (49)
Chapter 2


11 Pages
Unlock Document

York University
BIOL 1500
Tanya Da Sylva

BIOL 1500 CHAPTER ONE {SCIENTIFIC THINKING} {May2010} D EFINITION {Element} substance that cannot be broken down chemically into any other substances {Atom} an atom is a bit of matter that cannot be subdivided any further without losing its essential properties. From the Greek for indivisible {Atomic Mass} made up of the combined mass of all of its protons and neutrons. {Atomic number} corresponds to how many protons it has {Ions} are electrically charged atoms {Molecules} are groups of atoms held together by bonds {Covalent Bonds} are strong bonds formed when two atoms share electrons CHAPTER NOTES Everything is made up atoms. The chemistry that is the most important in biology revolves around a few important elements Whatever the element, if you keep cutting it into ever smaller pieces, each of the pieces behaves exactly the same as any other piece Everything around us, living or not living can be reduced to atoms o At the centre of an atom is the nucleus, usually made up of two types of particles called protons and neutrons. o Protons are particles that have a positive electrical charge o Neutrons are particles that have no electrical charge o The amount of matter in a proton or neutron, its mass is about the same. o An electron weighs almost nothing. Whirling around the nucleus of every atom are negatively charged particles called electrons Particles that have the same charge repel each other, those with opposite charges are attracted to each other So far 90 elements have been discovered that are present in nature, and 25 can be made in a laboratory The number of protons in an atoms nucleus determines what element it is (atomic number) o The number of neutrons is usually equal to the number of protons o The mass of the atom is about double its atomic number BIOL 1500 CHAPTER ONE {SCIENTIFIC THINKING} {May2010} Four elements make up more than 96% of your body o Oxygen (65%), carbon (18.5%), hydrogen (9.5%), and nitrogen (3%)reactive elements, combining and creating bonds with other molecules o Other 6 are calcium, phosphorus, potassium, sulfur, sodium, chlorine o Trace amounts of 15 other elements are also found in the body (less than .1%) Atoms electrons determine how the atom bonds with other atoms. The prescribed area electrons move around in-electron shell o First electron shell is closest to the nucleus and can hold 2 electrons. o The second shell is a bit farther away from the nucleus and can hold as many as eight electrons o Atoms became stable when their outermost shell is filled to capacity Desirable state? Full outer shell of electrons An atom with extra electrons becomes negatively charged, and an atom lacking one or more electrons is positively chargedion Molecules and compounds. It requires energy to build bonds and glue atoms together o When bonds are broken (i.e. through consumption) the energy is released that was used to create them o Molecules are created as a short-term storage of energy that can be harnessed later Covalent Bonds Strong bonds formed when two atoms share electrons Atoms are no longer likely to bond with other atoms when their outer shells are full The sharing of two electrons between two atoms is called a double bond (O)2 o Carbon has 4 electron vacancies and therefore can form (and often does) four covalent bonds (CH) 4 Covalent bonds form molecules Electron circles around both nuclei Ionic BondsBIOL 1500 CHAPTER ONE {SCIENTIFIC THINKING} {May2010} One atom transfers one or more of its electrons completely to another Since each has an unequal number of protons and electrons , each atom becomes an ion The atom gaining electrons becomes negatively charged, atom losing electrons becomes positively charged Ionic bonds form compounds o Two oppositely charged ions attract each other Ionic bonds are not as strong as covalent bonds as the electron circles around a single nucleus Hydrogen bonds Bond multi-atom molecules together Bond is based on attraction between positive and negative charges Attraction between slightly positively charged hydrogen atom of one mole
More Less

Related notes for BIOL 1500

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.