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REVIEW: Parts of the Atom Electron Orbit Neutron Proton Nucleus Element, Compound, or Mixture? ELEMENT COMPOUND ELEMENT MIXTURE COMPOUND MIXTURE Review of the Periodic Table What is the symbol for Titanium? Ti _________ What is the atomic number of titanium? titanium 22 Ti 47.867 22 _________ How many protons does titanium have? 22 _________ How many electrons does a neutral titanium atom have? 22 __________ What is the atomic weight for titanium? 47.867 _______________ The Periodic Table The Periodic table as we know it today was arranged by a Russian Chemist named Mendeleev. He arranged it according to the physical and chemical properties of the elements Author: J R Reid WORKSHEET 1 Complete the handout by writing the missing chemical symbols in each box. ON your periodic table following: Alkali Alkaline Metals Transition Metals Poor metals Halogens Noble gases Non metals (given last lesson) Label the halogens Arranging Elements It is arranged in rows (across) called Periods and columns (down) called Groups Groups of elements show certain trends – they have similar properties Groups Periods Trends On The Periodic Table Author: J R Reid Atomic Size Atoms have certain sizes depending on: The amount of electrons (negatives) The pull from the nucleus (positive protons) For the third period (row) the atomic radius for each atom gets smaller across the table Na Mg Al Si P S Cl Ar Even though the atoms have got more electrons their electronegativity (pull for electrons) is increasing because of increasing number of protons Electronegativity Electronegativity is the ability of a nucleus to attract its valence/bonding electrons. It follows certain trends on the table: As you go across (left to right) it gets stronger As you go up it gets stronger e- 11 12 Na e- eee- 13 e- e- Mg Al e- e- e- e- 14 e- e- 15 e- Si P e- e- 16 ee- 17 e- S Cl What do you notice about the atomic number as you go across the period? e- 19 e- What about the number of orbitals as you go across the period? What about the number of orbitals as you go down a group? e- K Ar e- Increasing size Size Trends From Left to Right Proton number and Atomic Mass increases Atomic size decreases (more protons pulling the electrons) Oxidising ability increases Form ionic compounds to forming covalent compounds Melting Points from relatively high to relatively low Form positive ions to form negative ions Trends down a group Proton number and Atomic Mass increases Atomic size increases (adding more orbitals) Metals become more reactive Non-metals become less reactive Valence Electrons Valence electrons (also known as valence) are the number of electrons present in the outer most orbital. What is the valence of this sodium atom? What is the valence of this chorine atom? Valence Electrons The number of valence electrons of an element is determined by its periodic table group in which the element is categorized.