SC4 - The Periodic Table ✓

Question 1

SC4a - How did Medeleev organise his periodic table?

Answer 1

By increasing atomic mass

Question 2

SC4a - What two things did Mendeleev do to the order of elements in his table that made it more sucessful than others?

Answer 2

• Left gaps for certain elements
• Swapped elements around
• He did this because he realised a trend in the chemical and physical properties in relation to the groups of elements

Question 3

SC4a - How did Mendeleev predict the property of elements such as eka-alluminium (now known as gallium)

Answer 3

He identified the trend in properties down a group and used this information to estimate the properties of undiscovered elements

Question 4

SC4b - Why does (in the modern periodic table) Tellerium come before Iodine despite having a greater mass number?

Answer 4

• Iodine exists mostly as Iodine-127
• Tellerium has many isotopes ranging from Te-126 to Te-130
• This means Tellerium’s Ar is ~128
• This proves one reason why it is more reliable to order elements by increasing atomic number than by mass number

Question 5

SC4b - How is the atomic number related to energy given off in x-rays when electrons are fired at an element?

Answer 5

• The square root of the energy given off is directly proportionate to the atomic number.
• This realisation proved the idea of protons and that the atomic number is the number of protons in an atom.

Question 6

SC4b - What are the four main features of the modern periodic table?

Answer 6

• Elements in a period are in order of increasing atomic number
• Elements with similar properties are in the same group
• Non-metals are on the right and metals are on the left
• The Iodine Tellerium pair reversal is explained

Question 7

SC4c - How do atoms store electrons?

Answer 7

• Atoms have electrons in orbits of electron shells around the nucleus
• The first shell holds up to 2 electrons
• The second and third shell holds up to 8 electrons

Question 8

SC4c - How do you work out the electron configuration of an element? Use Chlorine (Atomic number 17) as an example

Answer 8

• Atomic number 17 means 17 protons and thus 17 electrons. 1
• 7-2 is 15, 15-8 is 7, 7-8 is a negative number so there are 2 in the first shell,8 in the second and 7 in the third 2.8.7

Question 9

SC4c - How does the electron configuration of an atom relate to its position on the periodic table in terms of group and period?

Answer 9

• The total amount of electron shells will be the period it is in.
• The number of electrons in its outermost shell is equal to the group that it’s in.