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ATOMIC STRUCTURE

ATOMIC STRUCTURE. The Periodic Table. Demetri Mendeleev is credited for creating the first version of the modern periodic table

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ATOMIC STRUCTURE

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  1. ATOMIC STRUCTURE

  2. The Periodic Table • Demetri Mendeleev is credited for creating the first version of the modern periodic table • The periodic table is a chart showing all the elements arranged in columns in such a way that all the elements in a given column exhibit similar chemical properties • The periodic table is organized in order of increasing atomic number • The periodic is organized in…. • Columns called groups or families • Rows are called periods

  3. Metals, Non-metals, Metalloids *Aluminum is the only metal touching the stair case *Hydrogen is the only non-metal to the left of the stair case

  4. Properties of Metals, Non-Metals, and Metalloids Metalloids Both properties of metals and non-metals Non-Metals Do not conduct heat or electricity well Brittle Not easy to mold Metals • Lustrous (Shiny) • Malleable (can be hammered into thin sheets) • Ductile (can be pulled into wires) • Hard • Conduct electricity

  5. Periodic Families Lanthanides Actinides 1- Alkali Metals 13- Boron Group 16- Oxygen Group 2- Alkaline Earth Metals 14- Carbon Group 17- Halogens 3-12 Transition Metals 15- Nitrogen Group 18- Noble Gases

  6. Periodic Families • Elements in the same family have similar properties • Alkali metals are the most reactive metals • Halogens are the most reactive non-metals • Noble gases are inert (do not react)

  7. Where did all these elements comes from?! • All elements after hydrogen were created by nuclear fusion. • Nuclear fusion is a nuclear reaction in which two or more atomic nuclei collide at nearly the speed of light and join to form a new type of atomic nucleus. • This creates newer and larger elements. • All elements from He-U occur naturally due to nuclear fusion happening in stars. • All elements past U are manmade.

  8. Atomic Structure • Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. • The energy levels and shells together are called the electron cloud • Electrons in the outer most shell are called valance electrons • Valance electrons determine the behavior of an atom

  9. Valance Electrons By Family 1 8 2 2 3 6 7 4 5 *Valance electrons are electrons in the outermost shell

  10. Atomic Structure-Helium Shell proton N + - + N - neutron electron

  11. Atomic Structure *Amu stands for atomic mass unit

  12. The Structure of An Atom • Atoms are composed of protons, neutrons, and electrons • Proton - positive (p) Neutron - neutral (n) Electron - negative (e-) • Nucleus - protons & neutrons • Electrons - around the nucleus in an electron cloud

  13. The Periodic Table of Elements average

  14. Atomic Numbers • The whole number is the atomic number- This identifies the element • The number with the decimal is the average atomic mass • # of protons = atomic # • # of electrons = atomic # (if neutral) • #neutrons = Mass number - # protons • mass number =# of protons + # of neutrons • Mass # is mass of individual atom

  15. Practice • How many protons are in Zinc? • What is the atomic number of Calcium? • What is the average atomic mass of Oxygen? • How many neutrons are in Lithium? • How many electrons are in neutral Carbon? • Why do the number of protons equal the number of electrons in neutral atoms? • 30 • 20 • 16.00 amu • 4 • 6 • Electrons are negative and protons are positive. The charged must balance each other out.

  16. Ions • If an atom gains or loses electrons, it is called an ion • When an atom gains or loses an electron, its overall charge is no longer neutral • A positively charged ion is called a cation • Cations are formed by atoms losing electrons • A negatively charged ion is called an anion • Anions are formed from atoms gaining electrons

  17. Practice • If a sodium atom loses an electron, what will its charge be? • +1 • How many electrons are in the following? • Cl-1 • 18 • Ca2+ • 18

  18. Isotope Notation/ Nuclear Symbol Mass Number O the number of protons and neutrons in an atom 16 -2 Charge: the number of electrons lost or gained (+ lost and – gained) Do NOT write 0 for no charge 8 Element Symbol Atomic number the number of protons in an atom number of electrons = number of protons - charge *Nuclear Symbols ONLY contain WHOLE numbers

  19. Other Notation • You may also see the following format: • Element Name- Mass Number • Example: Oxygen-16

  20. Practice • Write the nuclear symbol for gold. • What is the mass of chlorine? • What is the atomic number of chlorine-35? • How many neutrons are in Uranium? • 238-92=146 neutrons • How many electrons are in Uranium below? • 92-3= 89 electrons +3

  21. Atomic Mass • The masses of protons, neutrons, & electrons are expressed in atomic mass units. It is abbreviated as amu. • The mass of a(n)… • proton is about 1 amu • neutron is about 1 amu • electron is almost 0 amu (1/1836 amu) • The mass number of an element is the # protons + # neutrons

  22. Isotopes • Isotopes are atoms that have the same # of protons (meaningit is the same element) but a different # of neutrons(meaning it has a different mass) • The difference between an element & its isotope is the mass number. Isotopes have a higher mass. • Place the isotope’s mass in the upper left corner of the chemical symbol of the element. Ex. 37Cl

  23. Average Atomic Mass • The mass number is the mass of one isotope • The average atomic mass is the mass of each isotope and how abundant it is in the universe • The average atomic mass depends on the abundance of each isotope • Abundance is the amount the isotope occurs in nature • For example: Abundance of Lithium • Lithium-6 is 7.59% abundant • Lithium-7 is 92.41% abundant

  24. Average Atomic Mass • Steps to calculating Average Atomic Mass: • Multiply the mass of each isotope by its percent abundance (remember %s are decimals; 85% as a decimal is 0.85) • Add you answers from number 1 together • Round your answer to 2 decimal places

  25. Practice You must show your work to use your notes on the Note Check! • A sample of Cesium is 75% 133Cs, 20% 132Cs, and 5% 134Cs. What is the average atomic mass? • 132.85 • Carbon-12 is 98% abundant and Carbon-14 is 2% abundant. Calculate the average atomic mass of carbon. • 12.04

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