periodic table

• How many chemical elements have been isolated and identified?


  Over 100
• How are elements arranged on the periodic table?


  In order of increasing atomic number
• What does each element on the periodic table have in relation to the element preceding it?


  One proton more
• Why are elements arranged in columns on the periodic table?


  To group elements with similar properties
• What are the vertical columns on the periodic table called?

  Groups
• What are the horizontal rows on the periodic table called?

  Periods
• What does a period indicate about an atom?


  The number of shells of electrons it has
• How are the periods numbered on the periodic table?


  From 1 to 7
• What does a group indicate about an atom?


  The number of outer electrons it has
• How many groups are there on the periodic table?


  7, plus Group 0
• What is the unique characteristic of helium in Group 0?


  It has only one shell with 2 electrons
• How does the group number help predict reactions of elements?


  It indicates the number of valence electrons
• Why do elements in the same group react similarly?


  Because they have the same number of valence electrons
• How can you predict the reactivity of elements in the same group?


  By observing the reactions of one element
• What happens to the reactivity of Group 1 metals as you move down the group?


  They become more reactive
• What happens to the reactivity of Group 7 halides as you move down the group?


  They show a decrease in reactivity
• Why is the term "periodic" used in the Periodic Table?


  Because similar properties appear at regular intervals
• How were elements arranged before the discovery of subatomic particles?


  In order of their atomic weight
• What did scientists notice when elements were sorted by mass?


  Patterns emerged at regular periods
• What was a limitation of the earlier periodic tables?


  Some elements were placed in the wrong group
• How did Mendeleev arrange his periodic table?


  By organizing elements into columns based on properties
• What did Mendeleev do when he found elements that didn't fit the pattern?


  He left gaps for undiscovered elements
• Why did Mendeleev switch the order of some elements?


  To maintain consistency down the columns
• How did Mendeleev predict the properties of undiscovered elements?


  By using the properties of other elements in the group
• What was one of Mendeleev's successful predictions?


  The existence of germanium, known as eka-silicon
• What limitation did Mendeleev's table have regarding isotopes?


  He made no provisions for them
• What is the modern periodic table based on?


  The atomic number of each element
• How can elements be broadly categorized?

  Into metals and non-metals
• How do metals achieve a full outer shell?


  By losing electrons to form positive ions
• What do non-metals do to achieve a full outer shell?


  They gain electrons to form negative ions
• What are metalloids?


  Elements that display properties of both metals and non-metals
• How does metallic character change across a period?


  It decreases from left to right
• How does metallic character change down a group?


  It increases as you move down
• What is an ion?


  An atom or molecule that has become charged
• What are cations?


  Positive ions formed by losing electrons
• What are anions?


  Negative ions formed by gaining electrons
• How does atomic size affect reactivity in metals?


  As atomic size increases, reactivity increases
• How does atomic size affect reactivity in non-metals?


  As atomic size decreases, reactivity increases
• What is the general electron arrangement for metals?


  1. 3 outer shell electrons
• What is the general electron arrangement for non-metals?


  1. 7 outer shell electrons