THE NATURE OF ATOMS SECTION A.3 CHEMCOM NUCLEAR RADIATION • Non-ionizing • ionizing SECTION A.3 CHEMCOM NUCLEAR RADIATION • Nuclear radiation • Radioactive decay • Alpha, beta, gamma SECTION A.4 CHEMCOM-RUTHERFORD TO BOHR SECTION A.4 CHEMCOM-RUTHERFORD TO BOHR ATOMIC STRUCTURE & MODELS WHAT MAKES UP AN ATOM? An atom is made up of subatomic particles (protons, neutrons, and electrons.) Protons and neutrons are made up of Quarks. An element is made up the same type of atom. What do you notice about the size of each type of particle? SUBATOMIC PARTICLES Subatomic Particles Charge Mass (amu) Location Proton +1 1 (very large!) nucleus Neutron 0 1 (very large!) nucleus Electron -1 .0005 (very very small!) outside nucleus What does an atom really look like? WHAT HOLDS AN ATOM TOGETHER? Because protons have a positive charge and electrons have a negative charge, they are attracted to each other because of the electromagnetic force (opposite charges attract, like charges repel.) PERIODIC LAW • Periodic Law a law stating that the elements, when listed in order of their atomic numbers, fall into recurring groups, so that elements with similar (chemical and physical) properties occur at regular intervals. Noble Gases ATOMIC STRUCTURE & THE PERIODIC TABLE OF ELEMENTS 1. What does the atomic number tell you? 2. How do you find the number of neutrons? 3. How do you find the number of electrons? BOHR MODEL Bohr Model can be used to show neutral atoms, isotopes and ions. It shows the basic subatomic particles in the atom. In the nucleus or center are circles. Each circle represents a single neutron and proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N. In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. ELECTRONS Electrons live in something called shells or energy levels. Only so many can be in any certain shell. The electrons in the outer most shell of any element are called valence electrons. BOHR MODEL PRACTICE So let’s try it…. How to draw a Lithium atom 1-Look at the Periodic Table 2-Determine the number of protons (Look @ the atomic number) 3-Then determine the number of neutrons (Atomic mass – atomic number) 4-Then determine the number of electrons (equal the number of protons in a neutral atom) 3 Li Lithium 7 BOHR MODEL LITHIUM Protons = 3 3 - Li - Electrons = Protons 2 in the 1st shell Lithium 7 1 in the 2nd shell ATOMIC MASS – ATOMIC NUMBER = NEUTRONS 7 3 = 4 - ISOTOPES An isotope is an atom that has the same number of protons, but a different number of neutrons. Isotopes of the same element have different mass numbers.. Elements have isotopes, the atomic mass listed on the periodic table is a weighted average of all the naturally occurring isotopes of an element. How to represent an isotope: Oxygen- 16 or 168O THE OCTET RULE •The octet rule states that atoms are the most stable when their outermost electron shell is complete, or has 8 valence electrons in it. •Atoms can achieve the octet rule either by gaining or losing electrons (forming ions). • Cations (Lose) = Positive Charge • Anions (Gain) = Negative Charge • Created by G.Baker www.thesciencequeen.net VALENCE ELECTRONS AND IONS • Since elements in the same group have the same number of valence electrons, they also form the same ions. POTASSIUM – BOHR MODEL K - K+1 - - - - - Ion - - - - - - - Neutral Atom - - - - - - - - 1 electron in outermost shell Protons = Electrons - - - - - - • 8 electrons in outermost shell Created by G.Baker www.thesciencequeen.net Cation Lost e- CHLORINE-BOHR MODEL Cl-1 Cl - - - - - - - - - - - Neutral Atom - - - - - - - - - 7 electrons in outermost shell Ion - - - - - Anion Gained e- - - • 8 electrons in outermost shell Created by G.Baker www.thesciencequeen.net
