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Atoms, Elements, and Molecules

Atoms, Elements, and Molecules. Image from: ase.tufts.edu. Matter. Matter is anything that has mass and takes up space Most of what we see is matter Matter is made of atoms What are atoms?. Atoms. Atoms are the smallest building blocks of matter that can chemically change

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Atoms, Elements, and Molecules

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  1. Atoms, Elements, and Molecules Image from: ase.tufts.edu

  2. Matter • Matter is anything that has mass and takes up space • Most of what we see is matter • Matter is made of atoms • What are atoms?

  3. Atoms • Atoms are the smallest building blocks of matter that can chemically change • This means that they are the smallest piece of matter that has chemical properties • Since atoms make up matter, and matter makes up almost everything we know, it means almost everything is made of atoms • Atoms are made of different parts

  4. Parts of the Atom • The atom is made of basic 3 parts: • Protons • Neutrons • Electrons Both found in the nucleus ‘Orbits’ outside the nucleus

  5. Parts of the Atom - Nucleus • The center of the atomis called the nucleus • It holds all of the massof the atom • There are 2 parts of the nucleus: • Protons – positively charged • Neutrons – not charged

  6. Parts of the Atom - Electrons • Electrons ‘orbit’ outside of the nucleus • Electrons are negatively charged • Electrons weigh about 2000 times less than protons or neutrons, so we assume the nucleus has all of the mass • Electrons orbit REALLY far away from the nucleus

  7. Electrons • Electrons are really far away from the nucleus • If the nucleus were the size of a marble and that marble was placed on the middle of a soccer field, the electrons would far outside the outside of the stadium. • This means that atoms are almost entirely empty space

  8. Atoms and Elements • There are different types of atoms • Each type of atom is called an element • There are 92 naturally occurring elements and 26 man-made elements • Each element has it’s own unique physical and chemical properties

  9. Elements • Elements are listed on the Periodic Table of Elements • Each elements has its own square on the Periodic Table • Each element has a 1 or 2 letter symbol called a chemical symbol • The first letter is ALWAYS a capital letter • The second letter (if present) is ALWAYS lower case.

  10. Chemical Symbol Examples • What elements have the following symbols? • C • Ne • Kr • Mn • Au • U • What are the symbols for the following elements? • Hydrogen • Boron • Oxygen • Magnesium • Einsteinium Carbon H Neon B Krypton O Manganese Gold Mg Uranium Es

  11. Elements and Protons • The number of protons tells us the type of element the atom is • The number of protons gives an atom its identity • Protons are abbreviated p+ • The number of protons in the nucleus of atom is the Atomic Number 8 O Oxygen • The atomic number MUST be a positive integer 16.00 Atomic Number = Number of Protons

  12. Element Examples • How many protons do the following elements have? • Oxygen • Fluorine • Titanium • Sodium • Silver • Which elements have the following atomic numbers? • 24 • 58 • 11 • 100 • 3

  13. Elements and Neutrons • Neutrons are uncharged particles in the nucleus • Neutrons are abbreviated n0 • When you add the number of protons with the number of neutrons, you get the Atomic Mass 8 O Oxygen 16 Atomic Mass

  14. Atomic Mass Atomic Number = Number of Protons • (# of p+) + (# of n0) = Atomic Mass • Eg. Oxygen • (# of p+) + (# of n0) = Atomic Mass • (8) + (# of n0) = 16 • (# of n0) = 8 • Oxygen-16 has 8 neutrons in its nucleus Atomic Mass 8 O Oxygen 16

  15. Atomic Mass Examples • What is the atomic mass of the following atoms? • Nitrogen with 8 n0 • Calcium with 20 n0

  16. Neutrons • Elements always have the same number of protons but can have different numbers of neutrons in their nucleus • The same element, with different numbers of neutrons are called Isotopes • Eg. All carbon atoms have 6 protons, but they can have 6, 7, or 8 neutrons. Carbon-6, Carbon-7, and Carbon-8 are all isotopes of carbon

  17. Atomic Mass Example • Eg. How many neutrons are in the following isotopes of Calcium? • Calcium-40 • Calcium-42 • Calcium-48

  18. Atomic Mass as an Integer • Since the atomic mass is the sum of 2 integers (number of protons and number of neutrons), the atomic mass is ALWAYS an integer • It is an irrational number on your periodic table it is because that is an average of the masses of isotopes

  19. Electrons • Electrons determine the behaviour of an element • They give an element its physical and chemical properties • The number of electrons is usually the same as the number of protons

  20. Electron Examples • What elements have the number of electrons? • 6 • 11 • 42 • 56 • 96 • How many electrons would the following atoms have? • Nitrogen • Helium • Potassium • Molybdenum • Bohrium

  21. Electrons • Remember when I said that atoms have the same number of electrons and protons… • That’s not always the case

  22. Electrons • Atoms can change their number of electrons frequently • This is because electrons are held loosely by the nucleus • This is also really important because if they couldn’t, we wouldn’t be alive!

  23. Electrons • Atoms are called neutral if they have the same number of protons and electrons • This is because if an atom have the same number of protons and electrons, the atom has no charge • Eg. – Hydrogen • Has 1 proton and 1 electron (+1) + (-1) = 0 No charge is neutral

  24. Ions • Atoms that lose or gain electrons are called ions • Ions have a charge • When writing the charge, it always goes in the top right-hand corner. • Eg. Fluorine with a -1 charge gets is shown as: F- • Eg. Selenium with a charge of -2 is shown as: Se2-

  25. Cations • If an atom loses electrons, it gets a positive charge • Atoms with a positive charge are called cations

  26. Cation Examples • How many electrons would each of the following have? • Beryllium loses 2 electrons • Sodium loses 1 electron 2) What is the charge on each of the following atoms? • Aluminum loses 3 electrons • Silicon loses 4 electrons

  27. Anions • If an atoms gains electrons, it gets a negative charge • Atoms with a negative charge are called anions • Think of it like this, A-Negative-ion, A-N-ion

  28. Anion Examples • How many electrons would each of the following have? • Fluorine gains 1 electron • Phosphorus gains 3 electrons 2) What is the charge on each of the following atoms? • Sulphur gains 2 electrons • Chlorine gains 2 electrons

  29. Can we go smaller? • If matter is made of atoms; and atoms are made of protons, neutrons, and electrons; what are protons, neutrons, and electrons made of? • How small can we go?

  30. Compounds • So far we learned about elements, 1 type of pure substance • The other type of pure substance is a compound • Compounds are 2 or more elements hooked (sometimes called bonded) together

  31. Compounds • Compounds are made of 2 or more combined elements • However, they have completely different chemical and physical properties than the elements they are made of • Example – Sodium is a silver metal that explodes when it touches water. Chlorine is a poisonous gas that destroys lung tissue. Sodium Chloride is salt and is necessary for life

  32. Chemical Formulas • Molecules are another name for compounds • All compounds are represented with a special notation • Write the chemical symbol of each element in the compound • If there is only 1 atom of that element in the compound, leave it alone • If there are 2 or more atoms of an element, write a small number in the bottom right hand of the chemical symbol

  33. Writing Chemical Formulas • Example – Write the chemical formula for Calcium Carbonate. It is 1 calcium, 1 carbon, and 3 oxygens. • Write the chemical symbol of each element • Ca C O • Write the number of the atoms in the bottom right corner of the chemical symbol • CaCO3

  34. Chemical Formula Examples • Determine which elements, and how many of each, are in the following compounds • BaCl2 • N2 • Fe2O3 • KCo2F5 • U3O8 • Write the chemical formula for each compound • Hydroiodic acid – 1 hydrogen, 1 iodine • Hydrogen Peroxide – 2 hydrogen, 2 oxygens • Glucose – 6 carbon, 12 hydrogen, 6 oxygen • Sulphuric Acid – 2 hydrogen, 1 sulphur, 4 oxygen

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