LEQ: Why is understanding the chemistry of atoms important to biology? Reading: 2.1 Activator: atoms Two-minute talk around your group and create a description of what an atom is Key terms: atom, element,

Atoms were formed billions of years ago. Origins: nebula hypothesis a nebula is an interstellar cloud of dust and gases supernovae “Star nurseries” Fast facts: Atoms are very ancient, forming billions of years ago in the big bang and the hot interstellar furnaces of stars. When a star explodes, scientist refer to this as a supernova, and this has a special implication for life. Atoms can spread across the universe in this fashion and the current thinking is that the atoms of your body and virtually everything around you came from one of these explosions In summary: Your atoms are on loan from stars They are extremely old – almost as old as the universe itself You are made of stardust by default. So you have that going for you, which is nice!

All living things are composed of atoms and their interactions. basic units of matter: small (picometer scale) Varied in size collection of particles interact through forces. Hydrogen atom (H) Oxygen atom (O) Atoms are the basic units of matter in our universe. They are extremely small (picometer = trillionth of a meter) Even on this scale they can vary in size. Hydrogen is extremely small when compared to large atom like sodium and is also less massive. Oxygen falls somewhere between them being less massive than atoms with larger atomic numbers, but greater in mass than a hydrogen atom. Atoms are mostly empty space, consisting of tiny subatomic particles which interact through forces.

Nucleus: Proton (minimum 1) Neutron (0-many) Electron (minimum 1) Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-) Every atom has an area where large particles called protons and neutrons can be found. Hydrogen is unique and the exception to this rule: a hydrogen nucleus consists of just a single proton (most of the time). Heavy elements like Helium, Carbon, and Oxygen contain increasingly greater numbers of protons and neutrons. Electrons are tiny subatomic particles found in areas outside of the nucleus called orbitals. Orbitals are not depicted in this figure, but a way of representing their associated energies is. Electrons occupying the outermost rings have higher energy states than those in the inner rings.

Protons determine the element (type of atom) (+) charge Neutrons - nuclear stability and decay: no charge Electrons participate in electromagnetism and bonding (-) charge Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-) Each subatomic particle has an associated charge property: Protons are positively charged (+) Neutrons are electrically neutral in charge Electrons are negatively charged (-) Each particle can be thought of as a par t in a system (the atom) that imbues it with characteristic properties: Protons are massive and interact with electrons (opposites attract in charge). They also determine the element, or type of atom Neutrons are associated with protons and nuclear stability or in the case where a nucleus is highly unstable – certain types of radioactive decay Electrons interact with protons through electromagnetism and generally stay within the realm of an atom except when chemical reactions occur. Electrons often move during chemical reactions.

Dozens of elements are essential to life. The list varies, but there are a few dozen elements common to life and a few that are absolutely essential. Here’s the shortlist: Hydrogen (H) – found in virtually all biological molecules and water Carbon (C) – the principle atomic building block of biological molecules like DNA Nitrogen (N) – an element extremely common in biological molecules including DNA Oxygen (O) – found in biological molecules, water, highly reactive Sulfur (S) – rarer, but essential for the structure of many proteins Phosphorus (P) – strange one associated with chemical reactions involving energy transformations in metabolism and DNA structure We will be adding to our list later.

Group: Design your own element Number of protons Number of electrons Neutrons? Atom Builder: http://www.pbs.org/wgbh/aso/tryit/atom/ If your atom is stable – describe its identity and properties If your atom is unstable, why? Correct your atom’s structure and then describe its identity and properties

Summary: What distinguishes one element from another? What three types of particles can be found in atoms? List a few of the most essential elements of life