Atomic Structure & Basics
Which two rows are often shown below the main periodic table and where do they fit in the table?
The lanthanides and actinides; they belong in periods 6 and 7, inserted after Group 2.
Name the three main types of elements
Metals, nonmetals, metalloids
Does atomic size increase or decrease across a period?
Decrease
Give one use of iodine or silicon.
Iodine—medical use; silicon—electronics
What two rows are shown at the bottom of the periodic table?
Lanthanides and actinides
Define lanthanides and give the typical atomic number range for these elements.
Lanthanides are man-made elements, numbers 57-71
Give one property of metals and one of nonmetals.
Metals conduct electricity; nonmetals do not
What happens to ionization energy across a period?
Increases
Why is sodium stored under oil?
It reacts with air and water
Are lanthanides metals or nonmetals?
Metals
Define actinides and explain why many actinides are not found in nature.
Actinides are elements that fill the 5f subshell; many are radioactive and unstable, so they decay quickly or are synthetically produced.
What group are alkali metals in and what charge do they form?
Group 1; +1
What element is the most electronegative?
Fluorine
Why do sodium and chlorine form NaCl?
Sodium loses an electron; chlorine gains one
Why are many actinides radioactive?
Their atoms are unstable
Explain why the lanthanides are sometimes called “rare earth metals” and describe one property they share.
They were once thought to be rare; they are shiny metals with similar chemical properties.
How are transition metals different from Group 2 metals?
Transition metals have many charges and higher melting points
Why do atoms get bigger down a group?
More energy levels and more shielding
Why are metalloids useful in electronics?
They control electric current
Why are lanthanides called rare earth metals?
They were once thought to be rare
What is element (Na)
Sodium
Why are noble gases not very reactive?
They have full octet
What element is larger in atomic radius? Magnesium or chlorine
Magnesium
Why is technetium-99m used in medical scans?
It has a short half-life and is safe for imaging
Why are these rows placed below the table?
To save space and group similar elements