Atoms, molecules, bonding, periodic table

Atoms Modern Atom Model Nucleus-Protons and Neutrons Electrons around nucleus, never know the true location

Protons Positively charged In nucleus

Neutrons Neutral (no) charge In nucleus

Electrons Negatively charged In orbitals, or an electron cloud around the nucleus

Elements Atoms make up elements The type of element depends on the atomic number, or the number of protons it has Most elements occur naturally, but some have to be created in a lab

Periodic Table Elements are organized on the Periodic Table according to atomic number and properties of the element

Hydrogen H

Atomic Number Number of protons Number of electrons

Symbol Universal abbreviations for the elements

Atomic Mass Mass of the protons and neutrons Each proton equals 1 amu and each neutron equals 1 amu Average number of neutrons in an atom = atomic mass – atomic number

States of Matter Solids, liquids, gases

Groups and Periods Groups = columns Share similar properties Periods = rows Atomic number, number of protons/electrons, and atomic mass increases from left to right

Groups Elements in the same column are in the same group Numbers on top indicate what group it is

Groups Noble gases-Group 18 Halogens-Group 17 Alkali metals-Group 1

Periods Row of elements is in the same period Only hydrogen and helium are in the 1 st period Number of protons increases from left to right Number of electrons in the outer shell of the atom increases from left to right

On Your Periodic Table Color the solids, liquids, and gases a different color Label groups and periods Make a key! Make sure you include: Atomic number Atomic mass Symbol Name

Valence Electrons Number of electrons in the outermost orbital Determine by the GROUP an element is in Determines how an atom will bond with other atoms

Valence Electrons con’t Group 1- 1 valence electron Group 2- 2 valence electrons Group valence electrons Group valence electrons All want to have 8 valence electrons in their outermost shell

Electron Dot Diagrams Show how many valence electrons an atom has Li Cl N

Practice Draw electron dot diagrams for the following atoms: Potassium Argon Sulfur Beryllium Carbon Bromine

Molecules When 2 or more atoms bond together

Ions Ions are charged atoms Happens when an atom gains or loses an electron Examples: Cl gains 1 electron so it becomes negatively charged, or Cl - Na loses two electrons so it becomes positively charged, or Na 2+

Ionic Bonding Atoms with 5,6, or 7 valence electrons usually become more stable when this number increases to 8 Atoms with 1, 2, or 3 valence electrons become more stable when they lose electrons Ions that have opposite charges will attract and bond together forming an ionic bond

Example Sodium has 1 valence electron Chlorine has 7 valence electrons If you combine them, Sodium will lose one electron and Chlorine will gain one electron. They both will be stable and have opposite charges so they will bond together. And you will have Sodium Chloride, or salt! We would name this NaCl.

Bond With A Classmate Each person has a card with an element on it. Decide if you want to give away some electrons or if you want to take some electrons from someone else. Find someone who wants to do the opposite and make a compound! On your paper, write the name of the person you bonded with, draw electron dot diagram of the bonding, write the ion charges (positive and negative charge on each atom)

Covalent Bonds Can oil and water mix? demo

Covalent Bonds Two atoms are sharing electrons Both nuclei are attracting the electrons, which holds the atoms together Molecules

Polarity Polar bond- electrons shared unequally, molecule becomes charged, like water Nonpolar bond- electrons shared equally, no charge on the molecule

Examples FF O H H

Metallic Bonding An attraction between a positive metal ion and the electrons surrounding it Metals lose electrons easily and form metal ions A metal crystal consists of positively charged metal ions embedded in a “sea” of electrons

Metallic Properties Good heat conductor Good conductor of electricity Most metals are flexible and can be shaped easily

Metallic Properties Vocab Ductile- Can be bent easily and pulled into thin wires Malleable- Can be rolled into thin sheets Luster- Shiny and reflective

Properties of Bonds Ionic- Hard, brittle crystals with high melting points, conduct electricity when dissolved in water Covalent- lower melting points, low boiling points, do not conduct electricity when dissolved