Chlorine, bromine, and iodine were grouped together in the earliest forms of the periodic table, including the table developed by Mendeleev. What was an organizing principle in this grouping at that time?

• Atoms of the three elements had approximately the same mass.

• The three elements react the same way with other elements.

• The elements have the same number of valence electrons.

• These three elements are all gases at room temperature

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NGSS.HS-PS1-1

The early periodic table organized the elements in periods of increasing atomic mass. What information is currently used to organize the elements on the periodic table?

• number of valence electrons 
• number of energy levels 
• atomic number 
• ionic radius 

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NGSS.HS-PS1-2

All elements found on the left side of the Periodic Table of the Elements have what properties in common?

• They conduct heat and electricity 
• They are all gases 
• They are brittle and dull
• They are radioactive

Which of these elements has an electron structure most similar to that of element X?

• 1

• 2

• 3

• 4

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NGSS.HS-PS1-1

Based on their locations in the periodic table, which element has chemical properties most similar to those of calcium, Ca?

• beryllium, Be
• potassium, K
• titanium, Ti
• yttrium, Y

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NGSS.HS-PS1-1

The number of valence electrons in an element affects the reactivity of that element. Which element listed has the fewest valence electrons?

• beryllium (Be)
• sodium (Na) 
• oxygen (O) 
• neon (Ne)

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NGSS.HS-PS1-1

NGSS.HS-PS1-2

According to the Periodic Table of the Elements, which set of elements has similar properties?

• H, C, I
• He, H, Al
• He, Ne, Ar
• Na, Ca, Al

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NGSS.HS-PS1-1

Hydrogen is a gas at a room temperature, but it is found with the alkali metals in group 1 on the periodic table. Which is the most likely reason hydrogen is grouped with alkali metals?

• All group 1 elements have the same number of protons.

• Alkali metals are gases at room temperature.

• Hydrogen is a metal.

• All group 1 elements have one valence electron.

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NGSS.HS-PS1-1

What is the family name of this group of elements? 

• Alkali metals 
• Halogens 
• Noble Gases 
• Alkali Earth Metals 

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NGSS.HS-PS1-1

NGSS.HS-PS1-2

Which element has 2 valence electrons? 

• cesium (Cs) 
• magnesium (Mg)
• boron (B)
• argon (Ar) 

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NGSS.HS-PS1-1