1 Fundamental Concepts of Atoms and Molecules DA 118 Radiology

2 (kinetic = motion, potential = stored) ; matter cannot be still. Everything has motion at the atomic level. Matter that is altered, energy happens. (kinetic = motion, potential = stored) ; matter cannot be still. Everything has motion at the atomic level. Matter that is altered, energy happens.

3 Matter –Matter is anything that occupies space and has mass. When matter is altered, the result is energy. Matter is always in motion. The atom is the most fundamental unit of matter. –Matter is anything that occupies space and has mass. When matter is altered, the result is energy. Matter is always in motion. The atom is the most fundamental unit of matter.

4 ATOM The atom is the smallest unit of matter. It consists of two parts: –Nucleus which is at the center of the atom. It contains protons and neutrons. The protons have a positive charge (+) The neutrons have a neutral charge. –Orbits which surround the nucleus carry electrons. Electrons carry a negative (-) charge. The atom is the smallest unit of matter. It consists of two parts: –Nucleus which is at the center of the atom. It contains protons and neutrons. The protons have a positive charge (+) The neutrons have a neutral charge. –Orbits which surround the nucleus carry electrons. Electrons carry a negative (-) charge.

5 The Basic Structure of an Atom

6 (+) Nucleus: is made up of protons (+ charge) and neutrons (no charge). Electrons: have a (-) negative charge

7 Nucleus The nucleus is the very dense center of the atom. The nucleus is very small in comparison to the size of the whole atom itself. If the atom were the size of a football field, the nucleus would be the size of the football. The nucleus is the very dense center of the atom. The nucleus is very small in comparison to the size of the whole atom itself. If the atom were the size of a football field, the nucleus would be the size of the football.

8 The number of protons, neutrons and electrons must be equal for the atom to be stable. Hydrogen is the simplest element with one proton, one neutron, and one electron. Tungsten (W) has 74 protons, 74 neutrons, and 74 electrons.

9 The Electrons The electrons are tiny, negatively charged particles that have very little mass.

10 Electrons The electrons travel in “shells” (labeled K-Q), around the nucleus of the atom. Think of it as a miniature solar system, where the planets are like the electrons, and the sun is like the nucleus. The electrons travel in “shells” (labeled K-Q), around the nucleus of the atom. Think of it as a miniature solar system, where the planets are like the electrons, and the sun is like the nucleus.

11 Electrons How do the electrons stay in their orbits?? The closer the shell carrying the electrons is to the nucleus, the stronger the attraction between the shell and the nucleus. Inner shell electrons have a stronger bond to the nucleus than outer shell electrons. This is called “binding energy” or “electrostatic force”. How do the electrons stay in their orbits?? The closer the shell carrying the electrons is to the nucleus, the stronger the attraction between the shell and the nucleus. Inner shell electrons have a stronger bond to the nucleus than outer shell electrons. This is called “binding energy” or “electrostatic force”.

12 Electron volts or kilo electron volts: the unit of measurement that the binding energy is measured in.

13 Atomic number: the number of protons in the nucleus equal the number of electrons and determine the atom’s number. Atomic number: the number of protons in the nucleus equal the number of electrons and determine the atom’s number. Atomic mass- the number of protons and neutrons combined is the atom’s atomic mass. Atomic mass- the number of protons and neutrons combined is the atom’s atomic mass. Atomic number: the number of protons in the nucleus equal the number of electrons and determine the atom’s number. Atomic number: the number of protons in the nucleus equal the number of electrons and determine the atom’s number. Atomic mass- the number of protons and neutrons combined is the atom’s atomic mass. Atomic mass- the number of protons and neutrons combined is the atom’s atomic mass.

14 Molecular Structure: the combining of atoms: A. by transferring of electronsA. by transferring of electrons B. by sharing of electrons between the outermost shells of atoms.B. by sharing of electrons between the outermost shells of atoms. A. by transferring of electronsA. by transferring of electrons B. by sharing of electrons between the outermost shells of atoms.B. by sharing of electrons between the outermost shells of atoms.

15 Ionization: The production of ions- converting an atom into an ion. The production of ions- converting an atom into an ion. – When an electron is removed from an atom in the ionization process, an ion pair is the result. The atom becomes the positive ion and the ejected electron becomes the negative ion. The production of ions- converting an atom into an ion. The production of ions- converting an atom into an ion. – When an electron is removed from an atom in the ionization process, an ion pair is the result. The atom becomes the positive ion and the ejected electron becomes the negative ion.

16 Ionization Radiation: Is radiation that is capable of producing ions by removing or adding an electron to an atom. Is radiation that is capable of producing ions by removing or adding an electron to an atom. – A. particulate radiation: travels in straight lines at high speed. – Electromagnetic radiation: travels as both a particle and a wave. Particulate radiation: travel in straight lines at high speeds. Particulate radiation: travel in straight lines at high speeds. Is radiation that is capable of producing ions by removing or adding an electron to an atom. Is radiation that is capable of producing ions by removing or adding an electron to an atom. – A. particulate radiation: travels in straight lines at high speed. – Electromagnetic radiation: travels as both a particle and a wave. Particulate radiation: travel in straight lines at high speeds. Particulate radiation: travel in straight lines at high speeds.

17 Molecules Atoms are capable of combining with one another to form molecules. A molecule is defined as 2 or more atoms joined by chemical bonds. Molecules are formed –By sharing electrons between the outermost shells of electrons –By the transfer of electrons from one atom to another Atoms are capable of combining with one another to form molecules. A molecule is defined as 2 or more atoms joined by chemical bonds. Molecules are formed –By sharing electrons between the outermost shells of electrons –By the transfer of electrons from one atom to another