Q1 · hard · AI-verified
An element has atomic number 20. Its oxide would be:
- Amphoteric oxide
- Basic oxide
- Neutral oxide
- Acidic oxide
Q2 · hard · AI-verified
A teacher asks students to identify the element with atomic number 19. A student correctly states its period and group. Which answer is CORRECT?
- Period 4, Group 1
- Period 3, Group 1
- Period 4, Group 2
- Period 3, Group 9
Q3 · hard · AI-verified
An element has the following properties: it is in Period 2, its oxide is basic, and it reacts vigorously with water to form an alkali. Which element is it most likely to be?
- Nitrogen (N)
- Lithium (Li)
- Carbon (C)
- Beryllium (Be)
Q4 · hard · AI-verified
Döbereiner's Law of Triads states that the atomic mass of the middle element is approximately the arithmetic mean of the other two. For the triad Li (7), Na, K (39), what is the approximate atomic mass of Na?
- 19
- 31
- 23
- 27
Q5 · hard · AI-verified
Dobereiner's Law of Triads states that the atomic mass of the middle element is approximately the arithmetic mean of the other two. Which of the following is a CORRECT Dobereiner Triad where the middle element's atomic mass closely matches the mean of the other two?
- Li (7), Na (23), K (39) — mean of 7 and 39 is 23
- Be (9), Mg (24), Ca (40) — mean of 9 and 40 is 23
- C (12), N (14), O (16) — mean of 12 and 16 is 14
- F (19), Cl (35.5), Br (80) — mean of 19 and 80 is 49.5