Question

I FILL IN THE BLANKS:
1.
showed that group
three elements called
triad had similar properties
2
arranged the known elements in the order of
their increasing atomic weight in the form of a table called Periodic
table.
3. In Modem Penodic Table, there are
horizontal
rows called
and
vertical
columns called
4. Valency of an element is either equal to the number of valence
electrons or equal to
minus valence electrons
5. Elements having the same number of valence electrons show
similar
properties.
II
TRUE OR FALSE:
1. Valency changes down the group
2. The elements of group 17 are called halogens.
3. The element X with atomic number 15belong to third period
and доир 15.​

Answer 1

Answer:

Explanation:

1.DOBEREINER

2. DMITRI MENDELEEV

3.HENTRY MOSELY

4.REPRESENTATIVE ELEMENTS OR S AND P BLOCK ELEMETS

5. Elements in the same column of the Periodic Table have the same number of valence electrons – that's why they have similar chemical properties. BORON AND SILICON

2

1. FALSE

2.TRUE

3.TRUE

HOPE IT IS USEFUL