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Science 7-7 Elements and the Periodic Table Name __________________________________ Date ___________________________________ Looking for Patterns in the Elements Matter is made up of about ________________________________________________ ______________________________________________________________________ Some elements are very ____________________________________________________ ________________________________________________________________________ Other elements are ________________________________ Others do not ____________________________________ at all. Mendeleev In the 1800’s, scientists began to suspect that the elements could be _________________ ___________________________________ By 1869, one Russian scientist, Dmitri Mendeleev, recognized a ____________________ ________________________________________________________________________ Medeleev studied the evidence, ______________________________________________ _______________________________________ Mendeleev’s Observations One of Mendeleev’s first observations was that some elements have _________________ _________________________________________________________ For example, Flourine and chlorine, are both gases that ___________________________ if you breathe them. Silver and copper are both __________________________________________________ Mendeleev believed that these similarities were _________________________________ __________________________________________________ To help him find the pattern, Mendeleev _______________________________________ ________________________________________________________________________ He kept track of all the properties he knew about an element including _______________ Atomic Mass Mendeleev also recorded two other important properties: ____________________________________ and ________________________________ Atomic mass of an element _________________________________________________ Atomic masses were determined by __________________________________________ ________________________________________________________________________ Bonding power ___________________________________________________________ Chemical bond was determined ______________________________________________ ________________________________________________________________________ The First Periodic Table Mendeleev tried arranging his cards on elements in various way s. He noticed that patterns appeared when the elements were ________________________ _______________________________________________________________________ He also discovered that the ___________________________________ of the elements from lithium to fluorine ___________________________________________________. Mendeleev discovered that arranging the elements by ____________________________ _______________________________________________________________________ He moved cards to positions where they _______________________________________ This left ___________________ blank spaces. Mendeleev proposed that the blank spaces would be _____________________________ _________________________________________________________. He even predicted their ________________________________________. Periodic In 1869, Mendeleev published the first _______________________________________ The word periodic means a ________________________________________________ In the modern periodic table, the properties of the elements _______________________ in each _______________ or ____________________________________. Within 16 years, chemists _____________________________ all three of the missing elements and named them __________________________________________________ Inside an Atom Deep within every atom is a core called a ___________________________. The model of the atom used today shows the nucleus as containing smaller particles called ______________________________________. Outside the nucleus are other particles, called _________________________________. Measuring an Atom Because atoms are so small, we cannot measure them with _____________________ __________________. Scientists created the ____________________________ to measure the particles in atoms. The mass of a proton or a neutron is about __________________________________ A proton has almost ____________________________________________________ which means that most of an atom’s mass is in its ____________________________ In the example, explain why the atom’s atomic mass is only 7 atomic mass units. Electrical Charges Protons and electrons also carry ___________________________________________ Neutrons are __________________________________________________________ Protons carry a ________________________________________________________ Electrons carry a _______________________________________________________ Electrons also _________________________________________________________ Atomic Number Every atom of a particular element contains the _______________________________. For example, every carbon atom contains ________ protons. Thus an element’s _____________________________________________________________________ _____________________________________________________________________ However, the atoms of an element may vary in the number of ____________________ They contain. For example a carbon atom may have ___________________________ This means that the ______________________________________________________ For this reason, chemists now organize the periodic table according to _____________ _______________________________________________________________ The Periodic Table of Today Although the periodic table is now arranged according to ________________________ ______________________________________________________________________ It now contains more than _________________________________________________ Reading the Periodic Table Each square of the periodic table usually includes the element’s ____________________ ________________________________________________________________________ Chemical Symbol for an element usually contains _______________________________ The last entry in the square is the _____________________________________________ ________________________________________________________________________ Organization of the Periodic Table An element’s properties can be predicted from its _______________________________ ________________________________________. As you look at elements across a row or down a column, the elements’ ______________ _______________________________________________________________________ This predictability is the reason why the periodic table is so _______________________ _____________________________________________. Groups The main body of the periodic table is arranged into _____________________________ _______________________________________________________________________ The elements in a column are called a ___________________________. Groups are also knows as _____________________________. The group is given a family _________________________________________________ The elements in each group, or family, have ____________________________________ For example, in Group 1 al of the elements are __________________________________ Periods Each horizontal row across the table is called a ___________________________. A period contains a ________________________________________________of elements from ___________________________________, just as a week on a calendar has a series of different days. Unlike the elements in a ___________________________________________________ Valence Electrons It is the electrons that explain _______________________________________________ because _________________________________________________________________ This is not true for _____________________________________________ When an atom has two or more electrons, they may be ___________________________ ____________________________ from the nucleus. Only the electrons farthest out can be _________________________________________ Electrons involved in transfer or sharing are called _______________________________ Bonding Power Elements may have _______________________________________________________ The number of valence electrons determines whether the electron ___________________ _______________________________________________________________________. The number of valence electrons an element has ________________________________ ________________________________________________. Valence Electrons in Groups Atoms that have the same number and arrangement of valence electrons have ____________________________ which is why the elements fall into a periodic pattern. The elements in each group of the periodic table have the _________________________ _______________________________________________ For example, each of the elements in Group 1, have atoms with_______ valence electron. In Group 18, each element except helium has atoms with_______ valence electrons.